late 14c., of a color, from rose (n.1) + -y (2), probably modeled on Old French rose. From 1590s of healthy complexions; 1775 in the sense "cheerful;" meaning "promising" is from 1887. Similar formation in Middle Dutch rosich, Dutch rozig, German rosig.
a rosy future
rosy predictions
rosin
Rosinante
roster
rostral
rostrum
rosy
rot
rotary
rotate
rotation
rotational