Complex sentence: It has been suggested that a surviving relic of Raeti's Latin speech is Romansh, a so-called "Rhaeto-Romance language", which survives today in a few valleys of Swiss canton Grisons (most of which is today German-speaking).
Split into simpler sentences: It has been suggested that a surviving relic of the Raeti's Latin speech is the Romansh, one of the so-called "Rhaeto-Romance language". Romansch survives today in a few valleys of Swiss canton Grisons (most of which is today German-speaking).