Rosicky, whose precise passing and ability to take on defenders makes the Czech side tick, missed the second half of Tuesday's 2-1 Group A victory over Greece due to the injury.
Team officials are sweating on whether the diminutive midfielder will be ready for the clash with the co-hosts Poland in which a win would guarantee a quarter-final spot.
Cech complained of a sore shoulder after the Greece match and had a precautionary scan but is fit to start.
"Petr Cech is doing light training today and Tomas Rosicky told me his Achilles is not as painful as it was yesterday," Czech spokesman Jaroslav Kolar said on Thursday.
"He is in the dressing room undergoing treatment."
Rosicky said on Wednesday he could barely stand on his injured foot but was still hoping to play in his team's final Group A match. Team doctors gave him a 75 percent chance.
The midfielder said he got hit in the same spot where he had experienced pain at the end of his club season with Arsenal but a scan showed no damage to the tendon.
Cech, whose blunder led to Greece's goal, played the whole game despite his shoulder problem but it has since improved and the keeper said he would be ready to play.
"I will be fine," Cech said. "I will 100 percent be ready for the match."
