Robben scored his first hat-trick for the Bundesliga side since joining from Real Madrid last August, while Croatia striker Ivica Olic and Germany's rising midfield star Thomas Müller both scored twice on Saturday.
Olic and Robben had both scored at Old Trafford a fortnight ago which knocked Manchester United out of the Champions League and put Bayern in the last four and Munich showed their form at home by dominating Hanover.
Olic put his side ahead on 22 minutes and Robben slotted a dream goal with half an hour gone before Müller put his side 3-0 up just before the break.
Olic and Robben then scored within a minute of each other soon after the restart and Müller showed his class with a superb individual strike on 62 minutes before Robben completed his hat-trick deep in injury-time.
Relegation-candidates Hannover barely had a chance to score and Robben said the thrashing was a good confidence boost ahead of the Lyon clash at Munich's Allianz Arena on Wednesday.
"It was a good game for our confidence, especially looking ahead to Wednesday and Lyon," said Robben, who has now scored 14 Bundesliga goals for Bayern this season.
"It was a very good performance, and we needed a good display too.
"We were poor against Leverkusen last week (in the 1-1 draw), but we were aggressive right from the start, we created plenty of chances, and we simply kept it up after going 2-0 up.
"We slowed things down a little in the second half, but we kept pushing forward, because we're aiming to win the league, and every goal can make a difference."
The win puts Bayern two points clear of second-placed Schalke with three games left in the German league and coach Louis van Gaal was happy with the performance, despite having claimed there were cissies in his squad before kick-off.
"I'm delighted with the way we let the ball do the work," said van Gaal. "That's the most important thing. If we do that, we have players who can make the difference, as we saw yet again."