Recalibrating for silver-oxide will work but not sure about the availability of 625 sized cells. But you could use a silver oxide cell with an adapter. Further, given that the meter in the Rollei 35 is not reading a specific spot in the field of view, I'm not sure that reading altered by a 1.5v battery would make that much of a difference. None the less, there are relatively simple ways to electronically compensate. Here's one example: http://www.rangefindercameras.net/weston.html
I don't know if recalibration would really work with alkaline cells as the voltage drops over time with alkalines. Some meter designs compensate for this and others do not. I don't know if the Rollei does.