The main problem going from Yamaha to Roland are the Mega voices. Anything relatively recent uses these extensively in the styles, and there just is NO decent Roland equivalent. If you use Roland's styles for Roland guitar patches, it's OK, and you've got the Guitar Mode, but (IMO) there is nothing on the Roland that can quite get the Mega Voice guitar sounds.
G70 to E80 is mostly transparent, but the other way round can be problematic. Some drum sounds and time-sliced 'phrases' just can't be easily duplicated.
But basically, if you have a Yamaha style that DOESN'T use Mega voices, the Roland Makeup (style/song header editing) Tools are the easiest to optimize a non-native style to work with the voices and drumkits.
And finally.... personally, I don't like many 'song-styles', or styles made from commercial SMFs. I just find them too recognizable, or a bit 'jerky' because there is rarely four bars on the same chord in each section to get a good groove going. Not to mention four bars of major, minor and seventh chords, to provide variation. Not to mention a variety of intros and outros, break/fills, etc..
There's a LOT more to making a decent, easily usable style than grabbing a few bars of an SMF (otherwise, we'd ALL be doing it!)....
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An arranger is just a tool. What matters is what you build with it..!