You won't find many properties eligible for USDA financing in Round rock. You will have to go east of 130 or north of 79. Some of the Round rock eligible communities are: Legends Village, Estates at Settlers park, Sienna, Paloma Lake and Valley Vista. If you want to be closer to Round Rock center but don't have money for down payment, you may want to consider applying for a down-payment assistance grant.
Please feel free to give me a call, to discuss eligibility for the DPA programs.
Good luck with your search and best regards,