Manuals in different languages

If I were to buy any manual made from the wizard of the coast on roll20, would it be possible to use them in a different language (given the fact that the manuals are already translated and available to purchase as physical versions on amazon and other sites)?

Unless the book was translated for Roll20, I do not think this is possible. To my knowledge, though character sheets and the site itself is available in other languages, the Wizards of the Coast books are available only in English.

I believe that to offer a book in another language would require a separate licensing agreement between Roll20 and the publisher of the alternate language edition (and possibly Wizards of the Coast would need to be involved, too). Even if such an agreement is struck, I believe it would be separate purchases for the user, just as buying the physical copy in different languages would be.