Roma, who lost their Europa League semi-final first leg 2-0 to German champions Bayer Leverkusen on Thursday, are fifth in the league standings after one win in three league games.

"We will find an angry Roma from Thursday who want to get back to fighting for the top-four positions and we will need a good game from our side," Allegri told a press conference ahead of Sunday's game in Rome.

"Roma are strong, they are doing very well. It will be a fascinating game, but difficult and complicated."

Juventus are third despite their dramatic decline in the second half of the season and victory on Sunday would secure their Champions League place.

Allegri's side lost once in the first half of the campaign, but have suffered four defeats in the second part and are on a run of one win in eight league matches.

"In the first half we scored 46 points, in the second half we didn't manage to do what we did in the first round, we've done much worse," Allegri said.

"We are close to the goal, and we need to stay focused. Until we have mathematical certainty, we need to be careful. Football always gives you surprises."

Daniele De Rossi has turned Roma's season around since taking over from Jose Mourinho in January, with the club ninth in the standings at the time, and Allegri was full of praise for the young manager.

"Daniele brought enthusiasm and light-heartedness, despite Mourinho's excellent work, in football you forget quickly, but Roma have played two European finals in two years," Allegri said.

"Daniele is young, he is just starting out and he can have a good career. I actually played with his father at Livorno, in 1986. Alberto's playing career was coming to an end, a wonderful person."

Serie A will have five Champions League spots next season.

Juventus have 65 points, one ahead of Bologna who have a game in hand, with Roma on 59. Atalanta are sixth, two points behind Roma with a game in hand.