My family has used all three - Roache, Roach, Roche - English language spellings of the name. It can also be de Rupe in Latin and de Roiste in Irish. One branch of the family even opted for DeRoche. There are, of course, additional variations in other languages, including French, Spanish and Portuguese. Roch is usually considered to be originally of Welsh origin, but again, no hard and fast rules apply.
Recently I have established a DNA study so that any male with the name Roache (and variations) can see if he has relatives in the database and, once he has his information, in other databases as well. Women can also follow their maternal lines using this technology. For information about how to be tested and for the related cost, see: http://www.familytreedna.com/surname_det.asp?count=3&group=Roachehttp://www.familytreedna.com/surname_det.asp?count=3&group=Roache