Hi Ashley,
Yardenman is correct, that strictly speaking Ranunculus is not an annual, but is a perennial that is not hardy in colder zones.
Ranunculus asiaticus is a geophyte. A geophyte is any species that forms modified plant organs for carbohydrate storage, including bulbs, corms, tubers, tuberous roots, rhizomes, and pseudobulbs. Many geophytes reproduce by the natural replication of their storage organs.
Ranunculus can have a tuberous root up to 1.5 feet (45 cm) long when mature. You could bring that indoors during the winter to keep it from freezing. You can grow Ranunculus from the tubers or from seeds. Growing them from seeds each year would be treating them like an annual. But the tuberous roots will be there in the Fall for the saving, if you are so inclined.
ZM