Well that's pretty much my question. The Roland s760 is a sampler made in 1990. I know both have the 9 pin connector.
this is the Roland MU1 mouse specs 8)
* Interface: MSX standard
* Sensor: optical rotary encoder
* Resolution: 30 pulses per rotation & 0.26mm per pulse
* Encoder speed: 120 r.p.m.
* Select switch operating force: 120 ± 80 gf
* Operating force mouse: 120 gf
* Input/output: TTL level
* Supply voltage: 5V DC ± 5%
* Outside dimensions: 97x64x38.5mm (WxDxH) max.
* Weight: approx. 110g w/o cable/connector
* Cable length: 110cm.
I realize this is an old post but for others needing the same information, the Amiga mouse isn't compatible with the Roland S-series but you can use an old MSX compatible mouse, or there are convertors you can build to http://synpro.heimat.eu/mousecon.htm
the other alternative is a software/hardware solution like sxxx http://synpro.heimat.eu/m_rc100.htm, hope that helps someone out there.