May 1st in Rothenburg, Germany

I would stay in Munich, there will be a lot more going on. It is indeed a "little" beer fest (still will probably feel plenty large) and it's fun to see the maypoles go up, etc.

Keep in mind it's also a federal holiday, so be prepared for almost all shops to be closed.

The city probably has a web site listing upcoming events.

I did a quick search for Maibaumaufstellen Rothenburg ob der Tauber and did not find much. Maybe best that you contact the tourist office. May Day will begin for many small cities in Bavaria with men guarding the May Pole with a fire and a lot of beer the night before, so it will not be stolen by neighboring cities that night. Stealing the neighboring cities May Pole is sport too. The May Pole will be put up the old fashioned way 1 May with poles and horses or modern with a farm tractor (with tractor sometimes days before). Beer factors in here a lot with a break and a schluck every 10 minutes or so. Sometimes a small city Fest, but no rides and such like an Oktoberfest. Usually there is a Dance in the evening of 1 May. With all the tourists in Rothenburg ob der Tauber there may not be much going on. In Munich I it looks like events across different neighborhoods. Maybe you check some towns outside Munich too. Some museums like Oberpfälzer Freilandmuseum have an old fashioned Maibaumaufstellen with Dirndl, Lederhosen, horses, poles, Bier and all.

http://www.maibaum-kalender.de/category/muenchen/

https://www.maibaum-aufstellen.de/termine-maibaumaufstellen-2018/

http://www.freilandmuseum.org/desktopdefault.aspx/tabid-236/230_read-1667/