* "Flower" sign then "Rose" sign: This is the most common way. You make the sign for "flower" (a "C" handshape moving up and down in front of your chest) and then the sign for "rose" (a "5" handshape moving down and then up in a circular motion near your cheek).
* "Many" sign then "Rose" sign: You can use the "many" sign (index finger tapping your chin repeatedly) followed by the "rose" sign to indicate multiple roses.
Remember that sign language is visual and often varies in regional dialects. It's always best to consult a qualified ASL teacher or interpreter to learn the most accurate signs for your area.