Brock picked off the Texans' Matt Schaub and ran 18 yards for a quick 7-0 lead and the 49ers (3-2) went on to score 14 more points off Houston turnovers, winning a second straight following two consecutive losses.
Frank Gore carried much of the offensive burden for San Francisco, gaining 81 yards with a score on 17 carries.
Schaub was picked off three times in all, going 19-of-35 for 173 passing yards before being replaced by T.J. Yates late in the contest for the Texans (2-3).
Arian Foster picked up 98 rushing yards on 21 attempts for Houston.
Notable deaths of 2014 [PHOTOS]
LeBron James reveals his new Nike shoes