The striker became Brendan Rodgers' first signing as boss of the Scottish Premiership side.
The 19-year-old became Brendan Rodgers' first signing since he took over at Parkhead. And his arrival means that he will spend the season playing alongside Roberts, who is on loan from Manchester City until the end of the campaign.
And having come through the youth ranks together at Craven Cottage, Dembele is excited at the prospect of linking up with the winger once again, this time for the Hoops.
"It will be nice to play alongside him again. I hope we can link up together. We grew up together at Fulham where we were doing some good stuff and I hope we can produce that again at Celtic," he told Celtic TV (via club's official website).
"I spoke to him before I joined Celtic and he told me about the club and everything. He just said it's a massive club and the fans are unbelievable and always behind the team. He also says that it's a good team that likes to play football and that's what I like to do, so hopefully I can help the team to progress."
If the pair take little time to re-establish that understanding that they would have developed during their days at Fulham, then it could enhance the Bhoys' chances of retaining their title enormously.
Roberts, also 19, was hugely impressive following his switch to the Scottish Premiership side, and added a creativity that was often lacking during the latter stages of Ronny Deila's tenure.
And if he is able to continue that form into the new campaign, and has a striker in front of him who has a good idea of what position to find when Roberts begins to take on the opposition full-back, then it seems highly unlikely that any team will stop the Hoops clinching their sixth league crown in a row.