The Astros acquired Robertson from the Blue Jays on Tuesday in exchange for Edinson Batista, Chandler Rome of The Athletic reports.
Robertson had been booted from Toronto's 40-man roster and now will report to Triple-A Sugar Land, where he will provide relief depth for Houston. The 26-year-old has made 27 appearances at the major-league level, compiling a 5.30 ERA and 40:11 K:BB in 35.2 innings.