They used the same letter for two sounds in the sense that it had a consonantal use and a vowel use. But they did not, themselves, perceive the two sounds as being different sounds. They are, to the Romans, one sound in two different contexts.

Quoting Vox Latina:

> There is also a much-quoted anecdote of Cicero's, which tells how, when Marcus Crassus was setting out on an ill-fated expedition against the Parthians, a seller of Caunean figs was crying out 'Cauneas!'; and Cicero comments [...] that it would have been well for Crassus if he had heeded the 'omen', viz. 'Caue ne eas'; this hardly makes sense unless, as we presume, the [consonantal] u of caue was similar to the [vocalic] u of Cauneas. A parallel case is provided by Varro's etymology of auris from auere

(The book is accurate in representing the Latin spelling as being identical for the consonant and the vowel; in fact they used V and U is a much later invention. Perhaps the book felt English speakers would have more trouble accepting V as a vowel than U as a consonant.)