Roberts arrives with plenty of experience in the English Championship after joining Doncaster in 2021.
The former Rygbi Gogledd Cymru (RGC) hooker passed a century of appearances for the Knights last month and will now get a chance to impress and earn a long-term contract with Dragons after signing until the end of the season.
“George arrived on Tuesday night from Doncaster and has trained really well, but there has been a lot of information for him to take in,” said head coach Filo Tiatia.
“He is committed to the opportunity and grateful for the chance. Elliot and James are a little while away so it was important we got some help and we are happy to have George here.”
Roberts made 103 appearances for Doncaster and scored 19 tries.
“He has been core to the team’s performances and has developed as an important leader within the group,” said Knights director of rugby Sir Ian McGeechan.
“We are delighted he has been given the opportunity to play in Wales for Dragons in the URC, something he has always wanted to achieve, and he goes with the very best wishes of all at the club to continue his journey towards a Welsh jersey.”
Coghlan is closing in on a return from a hand injury while Burrows is touch and go for the Lyon fixture because of a rib issue.
Dee (shoulder) and Benjamin (groin) are unlikely to feature before the Six Nations.