Juve meet Roma on Saturday night struggling at the start of this season.
Allegri said: “Tomorrow is the first direct clash against a Roma that is doing well and is continuing the positive trend of last year by winning the Conference League. Re-meeting (Jose) Mourinho is always a pleasure, he is doing a great job and shaping Roma in his own way.
"Tough team, has not yet conceded a goal. It will be a very balanced match.
"It will be a good match, an evening of sport and football. Juve-Roma remains, so there is attention and curiosity. We are only on the third day, we need to improve the condition, the management of the match. But what I want to say is that we must remain calm .
"Tomorrow the championship will not be lost, we are only at the beginning. Tomorrow we will need the fans, with Sassuolo they were extraordinary, there will be moments of difficulty where they will serve. We play against a Roma that at this moment it is strong. It will take help from everyone."
On facing Paulo Dybala, Allegri added: "We spent some extraordinary years, at Juve he grew up, he became the player he is, with his plays he made everyone have fun. Tomorrow we will find him again as an opponent, it is a pleasure to see him again."
