Round Rock is a great place to live and I wish you the very best with your move! You can visit my home search portal to look at homes in Round Rock for lease or purchase. Hope this helps!
You've picked a great place to come live. You can search specifically for homes that will go to Walsh Middle School but you are too early. Currently homes in the area are renting 13 days after they hit the market. If you want to keep track of what is going on and off of the market you can search by school here (and they will be current unlike on Trulia): http://www.sellanaustinhome.idxco.com/idx/16847/advancedSear
Good luck and Welcome to Round Rock!