The 6-foot-11 Dalembert agreed to a multi-year contract last week. The team officially announced his signing Monday.
Houston opens the season at Orlando on Monday night.
Dalembert averaged 8.1 points and 8.2 rebounds for Sacramento last season. He played his first eight seasons in Philadelphia after the 76ers made him a first-round (26th overall) pick in 2001.
The Rockets needed to add a big man after NBA Commissioner David Stern halted a three-team deal that would have brought Pau Gasol to town.