"rosy sky" is a correct and usable phrase in written English.
You can use it to refer to a sky that looks pink or reddish due to the presence of clouds or the sunset. For example, "The rosy sky at dusk was beautiful to behold."
The gnarled trunk, carefully shaded to give a sense of its age, and its white blossoms are smack up against the viewer's eye; seen through them are a warm rosy sky and a gray-green lawn.
F. Scott Fitzgerald wrote, in the essay "My Lost City," "I remember riding in a taxi one afternoon between very tall buildings under a mauve and rosy sky; I began to bawl because I had everything I wanted and knew I would never be so happy again".
The crops were jade green; the flowers were in bloom, releasing their perfume into the air; the skylarks sang in the rosy-red sky.
The sun is low and rosy, and the sky has that inscrutable maybe-it'll-rain look about it, shifting between pink, grey, white and blue.
Each canvas presents a wide, all-over satiny field of flat, curvy shapes painted in lovely Easter-egg hues: sky blues, rosy pinks, peaches, apricots, turquoise, lime greens, custard.
The sky was all rosy pinks and yellows, stunningly beautiful.
I looked: like morn slow-kindling in the skies A dawn of rosy cheeks and sunny eyes Enriched my vision.
Dawn is beginning to creep across the sky, the old stones taking on a rosy hue as the light begins to hit them.
The skyscrapers across the river were bathed in rosy light, and a rainbow appeared in the stormy sky just before the band took the stage and launched into "Lover's Eyes," an anthemic song off its long-anticipated second studio album, "Babel" (Glassnote), slated to be released next month.
Frost crunching underfoot, countryside crystallised beneath crisp skies, the joy of being scarf-swaddled, rosy cheeked and steamy breathed – there's nothing like a winter walk.
High up the sky is bruisy blue; at the horizon it's rosy; in between, clouds gather.
