Roma, who made light of the absence of suspended top scorer Mattia Destro, are five points behind Juve, who visit Udinese on Monday (1845).
Roma, who have five games to play, are hoping they can prevent Juventus clinching the title before the two sides meet at the Stadio Olimpico in the penultimate round of the season.
Taddei fired Roma into a deserved lead with a shot from the edge of the area in the 13th minute after they had dominated the opening exchanges.
A superbly-worked move produced the second goal just before halftime as Gervinho released Francesco Totti who chipped the ball over the defence for Daniele De Rossi to touch it into Ljajic's path for the Serb to sidefoot home.
Stalwart Totti was also involved in the build-up to the third goal in the 63rd with a backheel to Ljajic who put Ivorian Gervinho clear to finish off the move clinically.
Ljajic hit the post and Gervinho missed an open goal as Roma looked for a fourth but instead Atalanta got a consolation when Giulio Migliaccio outjumped Maicon to head in from 12 metres.
Serie A results
Sassuolo 1 - 1 Cagliari
Roma 3 - 1 Atalanta
- Sports & Recreation
- Adem Ljajic