Rumours that the Giallorossi midfielder is unsettled in the Italian capital grew louder when Zeman described him as "not integrated" in a midweek press conference, but ahead of Saturday's visit of Fiorentina, the Czech tactician reacted angrily to the conjecture.
When told that Viola boss Montella had laughed about making an audacious bid for De Rossi in January, Zeman told Gazzetta.it: "There's nothing to joke about.
"It's all misinformation, you've not reported the words that I actually said. It's not good at all that you've misinterpreted the words I said and their meaning.
"He's at my disposal and the 'not integrated' comment refers only to a tactical issue, because he is used to playing in a different midfield set-up.
"What would he be worth on the market? I don't know, but I can't imagine there are more than 10 clubs out there that could afford to buy him.
"I hope he can contribute as he's an important player, and there's nothing to clarify about his situation."
De Rossi returns to contention after serving a three-match ban, while Erik Lamela is closing in on a prompt comeback to action following injury.
Montella, who made almost 200 appearances for Roma, has guided Fiorentina to fourth place in Serie A since leaving his job at Catania this summer
The 38-year-old told Gazzetta.it: "Going back to the Olimpico will feel a lot different from most matches.
"Until now the biggest emotion I've felt was facing Catania, seeing as I'm still so close to the guys I coached last year.
"Roma are a top-level team. They've spent 100million euros over recent seasons and they have the best attack in Serie A.
"Zeman is a tactician who has made history and his footballing ideology continues to pay dividends. They play well in the channels, exploit the space and have great quality."
La Viola have been light on strikers over recent weeks due to injury but Montella is hopeful that Stevan Jovetic could play some part in Saturday's game.
"The lad is feeling better now," Montella added. "He's not trained a lot over the last month so I have to take that into consideration. I'd like him to be on the bench in Rome."
Sixth-placed Roma are now just three points shy of Fiorentina having won their last three league games.