It depends on the what genes your birds are carrying.
Rose comb can be RRpp or Rrpp and it would be easier to get rid of in the latter. Single comb is rrpp. Pea comb is rrPp or rrPP.
Cross your RRpp to rrpp you get Rrpp (all rosecombs). Cross Rrpp to rrpp, you get 50% straight combs (theoretically). At which point you could just get rid of the rosecombs, assuming all other characteristics are correct.
It would be the same with Pea Combs.
If you cross one of your rosecombs to a straight comb and get some straightcombs, then you know that rosecomb is Rrpp. However, if you don't get any straight combs, it doesn't necessarily mean that the rosecomb is RRpp, since it is all a matter of chance and expected outcomes are theoretical.
ETA what breed are you working with? I assume it is one that already comes in rose combs and straight combs.