Gardner, 29, hails from Barrow and has made more than 270 top flight appearances for Saints, as well as earning nine international caps for England and Great Britain.
Prop Walker will also join up with Dave Woods’ side, who travel to Keighley on Sunday in the Kingstone Championship.
Saints General Manager Mike Rush said: “We are indebted to Dave Woods and his team for allowing us the opportunity for our first team players to get valuable game time at a high level.
“Both Ade and Anthony will benefit from the match against Keighley as they look to force their way into Nathan Brown’s first team plans.
“We have real competition for places at the Saints and agreements such as this and with Rochdale enable our players to build up vital match fitness.”