Do you think Rohanne disappearing could be her leaving Gerold Lannister behind and do you think Webber, sellsword of the Windblown is her descendant? Do you think Rohanne and Dunk had a child together? Or are only Brienne and possibly Hodor and the Cleganes his descendants? How many children did Dunk father altogether? Do you think he slept with young Old Nan and/or one of Egg's sisters or cousins? Sorry, I just have so many questions.
No to almost all of these. I only read Aegon V and Duncan's tale once and barely remember it, but I have the impression Duncan wasn't that much of a ladies' man. While it's possible w/Brienne at least-- loneliness and all that--we really need to figure out the hypothetical woman who married a Tarth man and had a child not his but Duncan's.
And I do remember that he and Rohanne never ever had sex. Yes, Rohanne definitely left Gerold, I think she had enough of "duty" and finally felt like she could choose herself. Webber could be anyone really, there is no proof one way or another that he is her descendant. He could literally just be an Essosi rando who took the name to appeal to Westerosi clients.