[quote=Jackie I can't tell, but would guess, that the soloists are German. In some places, singing Latin, they actually rrrroll their r's. Is that correct?
[/quote]

Yes, indeed. Should be done in any variety of choral Church Latin. Some differences you will see in German Church Latin from the more often heard Italianate are "ts" for C before E, I, and Y, rather than the Italianate "ch", the pronunciation of GN as in "doG Nose" rather than the Italianate "ny" as in "caN You", and pronouncing initial S followed by a vowel as "z".