Buff orp is def looking roo. My mixed breed Welsummer hen was late maturing I’ll try to attach a photo. She had a rosy comb early on but underdeveloped. She is mixed barred rock tho. At over 1 year old her comb is massively large & red now; she lays brilliant chocolate brown eggs.
You can try 'tail flare technique’ to determine gender, which is where you gently hold your chickie firmly with both hands, faced away from you, holding wings down to prevent flapping/injury. Gently dip their head down, kinda quick like without letting go- if a pullet the tail will flare open like a fan. If a roo you get nothing, droopy tail stays put. Note that only roosters develop saddle/sickle feathers on their back. Roosters usually have pointed tail feathers, hens rounded off. good luck to you!