From Longman Dictionary of Contemporary Englishrosebud mouth/lipsrosebud mouth/lipsa mouth or lips that have a small round shape and are very red → rosebud
Examples from the Corpus
rosebud mouth/lips• Corrie had a short, snub nose and rosebud mouth, and her eyes were a smoky grey.• I looked down at the perfect rosebud lips, the determined chin and the tiny clenched fists of my cub.• The rosebud mouth was painted a glowing coral pink, an exotic contrast with her creamy olive skin, liquid dark eyes. 