When does Gandalf find out about Bilbo's ring?

Answer 1

The ring makes him invisible.

The dagger is an elven blade and glows in the presence of orcs and goblins.

Answer 2

This is a bit unclear as one could argue that Gandalf guessed that Bilbo had a magic ring almost the moment he heard the tale of Gollum after Bilbo escapes. We do not know when exactly he begins to suspect that the ring could be the ONE ring, but he finds out for certain in Fellowship of the Ring after testing it in fire.

Answer 3

He got lost in the mountain in gollums cave and then he found gollum and they had a riddle contest and then he found it on the ground and he asked what is in my pocket and then he put the ring on and ran to a door and escaped out of the mountains

Answer 4

Apparently by accident when The Ring slips on his finger and Gollum runs right past him as if he could not see him. Gandalf later speculates that The Ring may have deliberately put itself on Bilbo's finger to allow him to escape so The Ring could get out of the mountains and get a chance to return to Sauron.

Answer 5

The heart of the Mountain; The Arkenstone. Also a lot of gold

Answer 6

I do no know