The question is a bit unclear. Do you mean this to include the use of the verb rile, as in to rile sb up, or do you mean just the phrase precisely as you have presented it—riled up—and nothing else? I ask because riled up is an adjective. There's little point in continuing until this is clear.I have been trying to get a fix on the expression
Is it an idiom, a phrasal verb, neither or both.