Stay away from 2222 and in town Lamar and Burnet roads. Out East of Pfluegerville there are great rides through Coupland and New Sweden. I'm including a Gmaps link for a little 50 miler I've ridden a few times: http://www.gmap-pedometer.com/?r=3893179
Also, if you Google the last Rosedale ride (last weekend and a hoot), they have a similar 60+ laid out.

Have fun!