Red Roof Rocked For Rock 'N' Roll
We're local but stayed at the Red Roof Sat. night before the Rock 'N' Roll Marathon to avoid the traffic stress. The race starts on the "main" side of downtown but finishes at the Alamodome near the Red Roof. Upon check-in, the desk clerk asked if I was in the race. When I said "yes," he offered a late check-out without my having to ask. At no additional charge, mind you. Also no charge for parking which was nice! Race start was 7:30 and the Red Roof had breakfast going by 6:00 which made it easy to grab something on the way out the door. They also offered water bottles and bins of fruit both before and after the race. Paid twice the price last year to stay at the Grand Hyatt (not including the GH's $40 valet parking fee) where the staff was rude and unaccommodating. Much better effort by the Red Roof and can't thank them enough! 
On the downside, I might disagree with the "Downtown/Riverwalk" description as the hotel is on the "other" side of downtown, and I don't think there's Riverwalk access from the Red Roof. It's not far, though.