The Championship club will be followed by 3,500 travelling fans for the all-ticket fourth-round clash at Spotland.
And the boss believes their backing will be vital as he plots another win over League One opposition after putting out Port Vale in round three.
The winners will earn £90,000 from the competition prize fund as well as a place in Monday’s fifth-round draw.
Town, who could hand a debut to new German striker Collin Quaner, last reached the last 16 in 2012/13, winning 2-1 at Leicester City in a fourth-round replay.
Wagner, whose side are fifth in the second tier, said: “It’s great to be involved in the FA Cup - and we want to stay involved.
“We have to make sure we do, but we are aware Rochdale will be a tough opponent, especially at their home.
“But what happens depends on us, because we have to be focused and make our own details right.
“With a great away support behind us, this will be a proper cup-tie, and they will help us for sure.”
Because B teams don’t take part in the German Cup, the Port Vale clash was extra meaningful for former Borussia Dortmund second team boss Wagner.
“Everyone in Germany is aware of its history and stature.
“We are all ready to invest everything and try everything to be successful.”
While Quaner could feature for Town, Rochdale have signed Stoke City left-back or winger Joel Taylor on loan.