As you managed to spell & punctuate both breeds correctly (although you omitted the THIRD word of my breed’s name), you are presumably a little more intelligent than the average Y!A Asker (despite you being a descendant of folk who didn’t have the sense to stay on the ship until it reached Aotearoa…). Therefore you should know that there is a HUGE difference between your "Can" and the word you actually needed, which is "Will".

There are two VERY big flaws in your plan, plus a serious consideration that you have overlooked.

BIG #1:
As you’ve been told, it is close to impossible for one person to concentrate 100% on TWO pooches at once. That concentration is ESSENTIAL during the first week, when you are home 24/7 concentrating on Pup 100% while it is awake, so that you learn Pup’s timing & signals for such as "Wanna go toilet" and "Wanna BITE sumfing!" in order to PREDICT them and take INSTANT appropriate action. It is VERY IMPORTANT during socialisation (a misleading term – it involves safely – in the PUP’s opinion – udergoing "familiarisation-&-confidence-building" for every movement, reflection, scent, sight, sound & texture in your district, and must be completed before Pup is 13 weeks old, 16 at the latest). Trying to work with TWO pups in the same class (even if you handle one and a family member handles the other) is close to impossible when training in a proper training club’s weekly classes where YOU should be for about a year starting when Pup is 18-22 weeks old, so that YOU are coached to improve your awareness & skills..

BIG # 2:
Two pooches of the same sex CAN get on together, and are almost certain to do so prior to 9 or 10 months old. But from 10 months (an age at which under-trained pooches act like those turbulent tempestuous teenaged humans who rebel against every vestige of authority) through 3 years, a pooch’s "ranking status" is VERY important to it. But only within its OWN sex. A dog and a bit.ch can BOTH be #1 in its sex. But 2 dogs or 2 bitches can NOT.
The situation where 2 of the same sex get on is when:
(a) both are gammas (natural followers, with no wish to be a leader), or
(b) one is an alpha (natural leader), the other a gamma.
It is HELL if:
(a) both are alphas, or
(b) one or both are uppity betas (wannabe leaders but without the right bearing & instincts, it knows only how to bully, so constantly starts fights). Many ignorant people think that an uppity beta IS a dominant alpha. NO WAY! A true alpha almost NEVER has to fight within its pack.
And when it comes to domination fights, dogs are often satisfied with mere posturing as their starter (which gives an observant alert owner a chance to intervene), but bitches almost ALWAYS go straight in for the kill (or at least to cripple the opponent’s front legs)

CONSIDERATION #3:
If you have 2 pooches of the same age (regardless of sexes) they are almost certain to die at close to the same time. So much grief usually results in the humans vowing "Never again!"
People wanting to be 2-pooch households should NOT get their second pooch until:
•1• The first is FULLY trained, so that it will set a good example for the new pup to copy (dogs learn VERY quickly from their elders – much quicker than they do from humans. It’s because OUR ways of communicating are so different to a dog’s way of communicating).
•2• The first is neutered and healed. That way there is no rush to neuter either of them too young. Read the research reports (in the Links section of the first address below) about the possible side-effects of Neutering at various ages – they convince me that voluntary neutering should wait until at least 11-15 months old.
And preferably
•3• Wait until the elder is about half a life-expectancy apart.

? Add http://pets.groups.yahoo.com/group/The_GSD_Source to your browser’s Bookmarks or Favorites so that you can easily look up such as rescue groups, feeding, vaccinations, worming, clubs, teething, neutering, size, diseases, genetics.

? To ask about your pet’s breed, join some of the YahooGroups dedicated to various aspects of living with them. If you don’t know how, click my group’s hot-link then, in the centre near the top where it says [Search for other groups], type the proper name of the breed, (For a cross-breed, either use the one he/she is most like, or do separate Searches for each parental breed).
Each group’s Home page tells you which aspects they like to discuss, and how active they are. Unlike YA, they are set up so that you can have an ongoing discussion with follow-up questions for clarification. Most allow you to include photos in your messages.
Les P, owner of GSD_Friendly: http://pets.groups.yahoo.com/group/GSD_Friendly
"In GSDs" as of 1967
References :

Whether any two dogs will become best friends is up to the dogs. Whether they will get along and not fight depends on how strong of a packleader the human is. You should go to leerburg.com and research this issue. They have the most realistic information on the issue of multi-dog households that I’ve found elsewhere. Dogs fight when they sense a lack of leadership from the human and they feel one of them needs to step up and take a leadership role in the pack. Dogs live together peacefully when they get a sense that the leadership job is taken and they don’t need to worry about it.

The first step is recognizing that how the dogs interact and get together is not their fault, it is a direct result of how you raise and train them. Most households luck out and are blessed with VERY forgiving dogs who do well despite all the handler’s mistakes. Put two powerful breeds together and if either or both of them has dominant tendencies, you have ZERO room for error. What’s worse, in situations like what you’re considering dogs tend to learn undesirable behaviors from eachother as they mature when what you really want is to focus on YOU for guidance and direction.
References :

I am actually researching right at this minute as one of my foster pups has a real mess of an elbow which would mostly be genetic but also not helped by exercise and play on a slippy floor. If you do get a rottie then they need ongoing training and socialisation. I take mine even though I take classes. They need it. They also need dog experience or understanding and correct nurturing.

But in general and why? Getting two puppies at the same time creates enormous problems. House training becomes a nightmare. If both of them decide that they want to pee on the carpet at the same time, picking them both up and taking them out to finish off in the garden is almost impossible

When you take a puppy out into the garden to do its pees and poos, you must praise it when it does so. However if one dog is at the other side of the garden it’s impossible to watch them both. You might be praising one puppy for peeing while the other puppy is digging up your lawn and this puppy will think that it’s being praised for digging.

Another example is when you will want to praise one of the puppies for performing and the other puppy is chewing your foot, what do you say? How can you train two puppies without confusing them? With two puppies neither of them will understand your commands or your praise.

Apart from house training, there are other aspects of training to consider. Two puppies will bond, they don’t need you, they will want to play with each other, you are not important to them. Play training a puppy helps our puppy to bond with us. So what, the puppies think if it can play with another puppy why I should listen to my mum or dad. My puppies and my adult dogs don’t know that I am strict with them, I use the soft approach. Although I am laid back I am in charge. You will never be “in charge” if you get two puppies at the same time & the two pups usually rely on eachother, and not you, that’s a BAD bond.

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I’d get them a year apart, and then they’ll get along just fine.
References :
Responsible Briard Breeder