Oh I been through this many times when I try to Roleplay, like ether I'm not well known and/or I'm a literate Roleplayer while most of em are unliterates and semi-literates
My Roleplay posts when I'm on my TLK character mostly never get's spotted on Bonfire at the Hill where the TLK Roleplayers are, suppose because of the rapidly quick chat going up and up like Superman and/or because people are faking to be blind to see my post, that's why before I go Roleplaying, I say "Time to Roleplay... alone again".
But however even with me playing me new ESO, I seem to got some idea's to get people know your trying to be part of the Roleplay, for example this may be a little stalky-doodles, but suppose saying "Are you listening to my posts or not?" to the Roleplayers in the Roleplay, however there's gonna be pros and cons of it. If the Roleplayers in that Roleplay tells you that they don't need you right now(Suppose they don't want you to get in the way), don't try to get in with force, that could be like trespassing on a private property, so instead, search for another Roleplay to try to join in.
However in fanbases such as TLK, you can try to be part of the current Roleplay, but that'll take practice for you to be trusted by other Roleplayers so that they can listen to your posts.