In a large saucepan, combine boiling water and rosemary; cover and let stand for 15 minutes. Strain, reserving liquid. If necessary, add water to measure 1-1/4 cups. Return liquid to pan; add sugar and vinegar. Bring to a full rolling boil over high heat, stirring constantly. Add pectin, stirring until mixture boils. Boil and stir for 1 minute.
Remove from the heat; skim off foam. Add food coloring if desired. Carefully ladle hot mixture into hot half-pint jars, leaving 1/4-in. headspace. Remove air bubbles, wipe rims and adjust lids. Process for 10 minutes in a boiling-water canner.
Canning Altitude Jam-Jelly
The processing time listed is for altitudes of 1,000 feet or less. Add 1 minute to the processing time for each 1,000 feet of additional altitude.