Verified answer

I'd say it's more like

"Wait a sec, isn't my room here?"

It sounds to me like someone is showing him his room but he says "って俺の部屋ここじゃん", contrasting that his room is actually "here".

I don't know in what context this sentences stands, so I can't be really sure.

Any mistakes go on my account.

Hope I could help o/

in my room, here in my room, where in my room