Question: The Cohors I Raetorum equitata spoke a Latin-based language that comes from which area of Italy and Switzerland?

Context paragraphs:
Cohors II Alpinorum equitata: Cohors secunda Alpinorum equitata ("2nd part-mounted Cohort of Alpini") was a Roman auxiliary mixed infantry and cavalry regiment.  "Alpini" was a generic name denoting several Celtic-speaking mountain tribes inhabiting the Alps between Italy and Gaul, which were organised as the Tres Alpes provinces.

Cohors II Aquitanorum equitata c.R.: Cohors secunda Aquitanorum equitata civium Romanorum ("2nd part-mounted Cohort of Aquitani Roman citizens") was a Roman auxiliary mixed infantry and cavalry regiment.  It was probably originally raised in Gallia Aquitania in the reign of founder-emperor Augustus after the revolt of the Aquitani was suppressed in 26 BC.  Unlike most Gauls, the Aquitani were not Celtic-speaking but spoke Aquitanian, a now extinct non Indo-European language closely related to Basque.  The regiment was also known as "cohors II Biturigum".  The Bituriges were a Celtic-speaking tribe whose territory was included in Gallia Aquitania.  It is believed that when the Aquitani regiments were originally raised (probably in two series), some were made up of mixed Aquitani and Bituriges recruits.

Cohors III Aquitanorum equitata c.R.: Cohors tertia Aquitanorum equitata civium Romanorum ("3rd part-mounted Cohort of Aquitani Roman citizens") was a Roman auxiliary mixed infantry and cavalry regiment.  It may have been originally raised in Gallia Aquitania in the reign of founder-emperor Augustus after the revolt of the Aquitani was suppressed in 26 BC.  Alternatively, it may have been raised by emperor Claudius (r. 41-54) to replace regiments stationed in the newly annexed province of Britannia.  Unlike most Gauls, the Aquitani were not Celtic-speaking but spoke Aquitanian, a now extinct non Indo-European language closely related to Basque.

Cohors IV Aquitanorum equitata c.R.: Cohors quarta Aquitanorum equitata civium Romanorum ("4th part-mounted Cohort of Aquitani Roman citizens") was a Roman auxiliary mixed infantry and cavalry regiment.  It was probably originally raised in the Julio-Claudian era, perhaps under Augustus after the subjugation of the Aquitani in 26 BC.  Alternatively, it may have been raised in a later levy of Aquitani after 14 AD.  Unlike most Gauls, the Aquitani were not Celtic-speaking but spoke Aquitanian, a now extinct non Indo-European language closely related to Basque.  Some tribes in Aquitania were Celtic-speaking, however e.g. the Bituriges.

Cohors I Alpinorum equitata: Cohors prima Alpinorum equitata ("1st part-mounted Cohort of Alpini") was a Roman auxiliary mixed infantry and cavalry regiment.  "Alpini" was a generic name denoting several Celtic-speaking mountain tribes inhabiting the Alps between Italy and Gaul, which were organised as the Tres Alpes provinces.  The regiment was probably raised as one of 4-6 Alpini units recruited after the final annexation of the western Alpine regions by emperor Augustus in 15 BC.

Cohors I Raetorum: Cohors prima Raetorum ("1st Cohort of Raeti") was a Roman auxiliary infantry regiment.  It is named after the Raeti, a designation probably given to some Alpine tribes, which were part of the eponymous province Raetia et Vindelicum, later called simply Raetia.  It comprised much of modern Switzerland, western Austria and Germany south of the river Danube.  The Raeti originally spoke a non Indo-European language that seems related to Etruscan.  However, by the time their territory was annexed by Rome under founder-emperor Augustus (16 BC), they had become largely Celtic-speaking through contact with neighbouring peoples such as the Vindelici.  Finally, during the centuries of Roman rule, they became Latin speakers: their distinctive provincial "patois" survives today in the form of the Rhaeto-Romance languages.

Cohors III Alpinorum equitata: Cohors tertia Alpinorum equitata ("3rd part-mounted Cohort of Alpini") was a Roman auxiliary mixed infantry and cavalry regiment.  "Alpini" was a generic name denoting several Celtic-speaking mountain tribes inhabiting the Alps between Italy and Gaul, which were organised as the Tres Alpes provinces.

Cohors I Raetorum equitata: Cohors prima Raetorum equitata ("1st part-mounted Cohort of Raeti") was a Roman auxiliary mixed infantry and cavalry regiment.  It is named after the Raeti nation, which dominated the eponymous province Raetia, which comprised much of modern Switzerland and Germany south of the river Danube.  The Raeti originally spoke a non Indo-European language closely related to Etruscan.  However, by the time their territory was annexed by Rome under founder-emperor Augustus (16 BC), they had become largely Celtic-speaking through contact with neighbouring peoples such as the Vindelici.  Finally, during the centuries of Roman rule, they became Latin speakers: their distinctive provincial "patois" survives today in the form of the Rhaeto-Romance languages.

Rhaeto-Romance languages: Rhaeto-Romance, or Rhaetian, is a traditional subfamily of the Romance languages that is spoken in north and north-eastern Italy and in Switzerland.  The name "Rhaeto-Romance" refers to the former Roman province of Rhaetia.  The linguistic basis of the subfamily is discussed in the so-called Questione Ladina.

Sidi Said, Morocco: Sidi Said, Morocco is a hamlet in Morocco located at 28° 27' 36" North, 10° 34' 12" was during the Roman Empire on of five Castra (fort) that guarded the city of Volubilis from incursion over the nearby Limes Africanus.  Sidi Said was the base for the Cohors IV Gallorum equitata, an auxiliary cavalry unit from Gaul.  Rome's control over the area ended, however, following the chaos of the Crisis of the Third Century, when the empire nearly disintegrated as a series of generals seized and lost power through civil wars, palace coups and assassinations.

Supporting paragraphs: Cohors I Raetorum equitata Rhaeto-Romance languages
Answer: north and north-eastern Italy