What are the rules about posting in other subs?

Hi, just wanted to know what the general consensus was here about how you feel about people posting their own examples in other subs. I saw this post in r/roastme, and I think this woman is really beautiful. I would love to post it, and I know it is no problem to do so in this sub, but I just wanted to see if anyone thought it was rude to post it here. What do you think?