The striker, who scored 16 goals last season including a double against Bradford in the play-off semi-finals, has been offered a new contract but has yet to sign.
Rowett is keen to get the matter resolved so that he can look at replacing the 28-year-old should he opt to leave the Pirelli Stadium.
"We made Calvin an offer, which probably wasn't what he was looking for after feeling he had a good season - which he did," Rowett told the club's official website.
"But there is always restraints on what we can offer people and Calvin is one of the top earners.
"He's gone away and had a chat with one or two clubs who are interested in him but he's going to be sought after - he's a very good striker who is 6ft 4ins tall and in our division there aren't many of those about.
"I've had a good chat with him and told him I really want to keep him and that I'll do everything I can to keep him but ultimately it's going to be his decision.
"He either chooses the love and affection we have for him or he carries on looking.
"We really need an answer from Calvin this week so that we don't miss out on other targets should he choose not to re-sign."