Here are some examples of exceptions mentioned by Mister Micawber: The adjectival form of romance is romantic. Academic and sarcastic stem from academy and sarcasm respectively.
Of course there are other ways to make adjectives from nouns, Nikoo, but that is not the question here. The question is whether -ly makes an adjective of a noun when it can attach to a noun. We are not concerned with the other suffixes here.