Brock Lesnar is not advertised for WWE Raw for the next two weeks after appearing the past two weeks. He is advertised for the February 25th episode in which The Rock is not being advertised.
It certainly looks like WWE is using Lesnar on Raw when The Rock isn't able to appear. The only episode where both Lesnar and Rock are being advertised before Wrestlemania 29 is the April 1st show from the Verizon Center in Washington, D.C.
Obviously this is subject to change but WWE is rotating the part-time talent so they either have Lesnar or The Rock on shows leading up to Wrestlemania.