LATIN IDIOMS

Romanian

Roman Province: Dacia

One of the changes to Vulgar Latin made in Romania was that an unstressed 'o' became 'u,' so you may see Rumania (the country) and Rumanian (the language), instead of Romania and Romanian. Romania is the only country in the Eastern European area that speaks a Romance language. At the time of the Romans, the Dacians may have spoken a Thracian language. The Romans fought the Dacians during the reigns of Trajan who defeated their king, Decebalus. Men from Dacia became Roman soldiers who learned the language of their commanders -- Latin -- and brought it home with them when they settled in Dacia upon retirement. Missionaries also brought Latin to Romania. Later influences on Romanian came from Slavic immigrants.

Reference: The History of the Romanian Language.

Italian

Italian emerged from further simplification of Vulgar Latin in the Italic peninsula. The language is also spoken in San Marino as the official language, and in Switzerland, as one of the official languages. In the 12th to 13th century, the vernacular spoken in Tuscany (formerly the area of the Etruscans) became the standard written language, now known as Italian. A spoken language based on the written version became standard in Italy in the 19th century.

References:

Italian - Language Information and Resources
Portuguese

Roman Province: Lusitania

Orbilat says that the language of the Romans practically wiped out the earlier language of the Iberian peninsula when the Romans conquered the area in the third century B.C. Latin was a prestige language, so it was in the interest of the population to learn it. Over time the language spoken on the west coast of the peninsula came to be Galician-Portuguese, but when Galicia became part of Spain, the two language groups split.

Reference: Portuguese: a Linguistic Introduction, by Milton Mariano Azevedo

Gallician

Roman Province: Gallicia/Gallaecia.

The area of Gallicia was inhabited by Celts when the Romans conquered the area and made it a Roman province, so the native Celtic language mixed with Vulgar Latin from the second century B.C. Germanic invaders also had an impact on the language.

Reference: Galician

Spanish (Castilian)

Latin Term: Hispania

The Vulgar Latin in Spain from the 3rd century B.C. was simplified in various ways, including the reduction of cases to just the subject and object. In 711, Arabic came to Spain via the Moors, and as a result, there are Arabic borrowings in the modern language. Castilian Spanish comes from the 9th century, when Basques influenced the speech. Steps towards its standardization took place in the 13th becoming the official language in the 15th century. An archaic form called Ladino was preserved among Jewish populations forced to leave in the 15th century.

References:

Catalan

Roman Province: Hispania (Citerior).

Catalan is spoken in Catalonia, Valencia, Andorra, the Balearic Isles, and other small regions. The area of Catalonia spoke the Vulgar Latin but was influenced heavily by the southern Gauls in the 8th century becoming a distinct language by the 10th century.

Reference: Catalan

French

Roman Province: Gallia Transalpina.

French is spoken in France, Switzerland, and Belgium, in Europe. The Romans in the Gallic Wars, under Julius Caesar, brought Latin to Gaul in the 1st century B.C. At the time they were speaking a Celtic language known as Gaulish. Germanic Franks invaded in the early 5th century. By the time of Charlemagne (d. A.D. 814), the language of the French was already sufficiently removed from Vulgar Latin to be called Old French.