"I would like to visit another town/area for two days."
Rothenburg doesn't take long. But you may want to skip it anyway, it's a beehive of international tourists and the folks that sell them stuff. People will tell you to stay overnight there because of the mood after the tourists go home. But I just don't get visiting a place that isn't so pleasant during the day. If you're thinking of R'burg as a travel base for seeing another town on Day 2, it's possible, but it's a somewhat weak travel base - it's located at the end of a trunk line and requires more time.
My suggestion: Take the train to Würzburg for 2 nights. Würzburg is a handsome city and a train hub on the Main River, a place with some good sights and a nice atmosphere. If you decide to see Rothenburg, you could go there on a day trip - it's about 1 hour from W'burg. But there are also some other nice smaller places very close to Würzburg that you could visit by train in addition to, or instead of, Würzburg and Rothenburg. All are less than 30 minutes from Würzburg.
Iphofen - see photos: http://www.stadtbild-deutschland.org/forum/index.php?thread/2985-iphofen/&s=40dacccc211fd7c6dae92d629101a55ce5e9a8e0
Marktbreit - https://upload.wikimedia.org/wikipedia/commons/3/3e/Marktbreit_BW_6.JPG
Ochsenfurt - https://upload.wikimedia.org/wikipedia/commons/4/4d/Ochsenfurt_am_Rathaus.JPG
Video that includes Marktbreit and Ochsenfurt - https://www.youtube.com/watch?v=VLUgpoQIFHI
With a Würzburg base, you can decide LATER what interests you most.