For some people, stretch tuning sounds more natural. It rarely ever sounds like notes are out of place. I would guess that someone has mucked up the tuning way past typical stretch tuning. You really shouldn't notice it as wrong notes, just a different timbre to the instrument.

I'm guessing that you can reset this to a lesser amount. Do you have the manual for the Roland? If not, there are web resources for some Roland products that will allow you to download the manual. The HP 245 model allows you to turn the stretch tuning on and off, and I'm guessing there are some that allow you to vary the degree of 'stretch'.

-Scott