I did a little reading recently regarding combs - for my own project work - and here is what I found which "might" be helpful to your question? This needs checking/confirmation by some of the more experienced breeders please!
Single Comb = denoted by a - or + (to show neither of the other genes are present)
Rose Comb = denoted by a capital R
Pea Comb = denoted by a capital P
Single = recessive to all other comb types
Rose and Pea Comb are dominant over Single
Rose and Pea Comb can express "together"
A bird receives a comb gene from each parent so we write their comb type as a pair of letters (one from mom and one from dad) as follows:
- / - = Single Comb (no rose or pea genes present)
R / - = Rose Comb (One copy of Rose only)
R / R = Rose Comb (Two copies of Rose)
P / - = Pea Comb (One copy of Pea only)
P / P = Pea Comb (Two copies of Pea)
P / R = Walnut or Cushion Comb (One copy each of Pea and Rose that BOTH show together). Walnut or Cushion is often like a rose comb but without the rear V point.
The answer to your question above (sort of) is that your comb options depend on which of the Pea and Rose genes you have in your breed. If you have rose and single combs in your flock now then you could introduce Pea by breeding to a type that commonly has Pea combs
My understanding, based on above reading, is that other features of the bird (like a crest for example) can alter the appearance of the comb, making it more or less pronounced. And there may be other genes that "modify" the look of the above comb types - like some that look "dubbed" or have "no points".