Financial terms of the deal, announced Tuesday, weren't revealed.
The 23-year-old Galiardi played only 35 games last season because of wrist and forearm injuries. He finished with seven goals and eight assists. The Avalanche selected Galiardi in the second round of the 2007 draft.
Rissmiller, 32, played for five teams last season, including the Lake Erie of the American Hockey League. He was originally signed by the San Jose Sharks in June 2003 and has played in 192 NHL games.
There was a lot of talk off the ice. From a player's standpoint, that's not the talk in the room. GMs make decisions, coaches make decisions, but as a team you have to come together and be ready to go, and we are.
— San Jose Sharks forward Tommy Wingels on his team's approach entering training camp