The Los Angeles Lakers have also shown interest in Lowry.
The Miami Heat contacted Lowry but have not yet set up a meeting or progressed talks, sources said.
Retaining Lowry is a top priority for the Raptors, who met with Lowry on Tuesday. He led them to their first playoff bid since 2008 this past season.
The Rockets met with Lowry just after midnight at the start of free agency. Houston is hosting Carmelo Anthony for a visit on Wednesday.
Lowry played for the Rockets from 2008-12.