The Italy international midfielder has been linked with a move to Premier League champions Manchester City despite signing a five-year contract in February this year.
However, Zeman, who replaced Luis Enrique as the Roma tactician after the 2011-12 season, is preparing his team with De Rossi in it.
"He is in good shape and I still have to decide on his tactical position, as it'll depend on the opponents we face each time," he said at a press conference on Saturday.
Zeman is also confident that he has an assembly of players who can compete for top honours this season.
"The new players we brought in can do a great deal for Roma, so I am very happy with the transfer strategy," he added.
"I am already happy with the squad, even if we don't bring in anyone else. Roma are competitive, although if we are to reinforce, then we can do so in every area of the team.
"I have a lot of faith in this squad and I am convinced we can challenge anyone."
Roma will begin their Serie A campaign against Catania at the Stadio Olimpico on the weekend of August 25-26.