Lohan hit the Roosevelt Hotel around 1:45 AM this morning ... where her ex-GF Samantha Ronson was hanging out.
Just 45 minutes later, the twosome ... who arrived in separate cars ... were seen leaving in the same ride.
Lohan has insisted the two are just good friends ... nothing more, nothing less.
You buyin' it?
UPDATE: Before you answer that last question ... check out what Sam tweeted early this morning.