Many of the current maps were made by Stealth, and he'll let you use them. Rolken wanted to eventually get better-quality, non-watermarked maps, and if those ever turn out then you could use those as well.
Okay, I fixed your message.
In case you also wanted to use my Sonic Adventure maps, leo03,
I don't mind. I guess credit isn't even really needed.
(You could say "from The Sonic Center" for them, though.)
They already have my name and picture in the corner, anyway.