There will be nearly 10,000 empty seats, even though prices have been slashed due to the low demand. An adult ticket will still cost £36, with children and OAPs able to watch European football for £18.
Mourinho said: "If we have Barcelona, Real Madrid or Inter Milan it's sold out. People don't look at Rosenborg in the same way as I look at them. The normal fan probably thinks it's an easy job, but I don't agree. The prices are not the best for them.
"The motivation for the fans is the Premiership and the latter stages of the Champions League. They don't look at the group stages with the same importance."