Hi Brad,
Welcome to the forum and the wonderful world of rottweilers....
Personally, I agree with Nisha'smum, at this stage in your life I dont think a puppy wouldn't be the best way to go, but that is MY opinion, this is your life and you are the one who has to make the time (I'm a stay at home mum so i have plenty of time to have a puppy). They need a LOT of time and attention and they also need time to bond with you, which they cant do if you are at work for 8 hours. Is this just Mon-Fri or do you work W/E also? Some COE breeders wont even sell you a puppy if you aren't going to be home for the majority of the day, those, undortunately, are the cold hard facts.
If you do decide to get a puppy, can someone come to your house and walk him/her for you during the day, take her out to go pee and poop or come and just play with it (friend/mum)? I would also highly recommend that you buy a crate to keep her in when you aren't at home. Fill the crate with her toys, a stuffed frozen kong, plenty of water and a nice bone.
Puppies also cant hold their bladder as long as grown dogs so there will be messes, LOTS of messes if you aren't home (suggest you get a puppy pad from the petshop).
Personally, I dont think the size of the yard matters all that much as long as your dog/pup gets regular exercise. I am on 1 and 1/4 acres and my 5 month old pup get walked 4 times per day for 30 minutes.
Puppies are great escape artists so if you must have her outside while you aren't home, definate build a run and make it secure. I'm from OZ also and i know that its different here, dogs are outside and we dont have the issue of the dogs being poisioned, taunted or murdered (esp in Perth, you dont even have more than 5000 in perth, do you????
Just kidding!!!) If you do have your dog run make sure there is plenty of water. Perhaps you could get something that automatically tops up the water. (Larger dogs dont usually tip over buckets of water, but puppies often spill their bowls of water) if you are going to be gone for more than 8 hours and your dog spills its water it could become dehydrated, esp in WA where your temperature get quite hot.
No matter what you decide to do, just make sure that the puppy is well exercised, both physically and mentally. A bored puppy will turn into a distructive dog.
Good luck with whatever way you decide to go!!!
Trina