Gareth Edds and John Welsh put Rovers into a commanding lead and although Glenn Murray pulled a goal back from the spot, before being shown a second yellow card, it was the home side who were left celebrating only their third league victory of the season at the final whistle.
Slade said: "I am bitterly disappointed with the result. I don't think we clicked into gear until the second period. But we had chances to score and did not put them away. Tranmere had only three opportunities and scored from two of them.
"We should have got something from the game but we made it difficult for ourselves and it was a ridiculous sending off for us - the referee was left with no alternative.
"We must not wait for things to happen. We can't wait until the opposition scores before we start playing. I am very frustrated.
"We have go to go back to the training ground. We need to get together and get back on track as quickly as we can. We are up and down at the moment and I know we are capable of a lot better."