Bring the water to a boil in a medium saucepan; remove from heat. Add petals; cover, and steep for 30 minutes. Strain liquid into clean saucepan. Discard petals.
Add sugar and lemon juice to pan. Bring mixture to a boil, stirring, over medium-high heat. Boil 2 minutes; add pectin, and boil 2 minutes (for firmer jelly, boil up to 2 minutes more). Remove from heat, add rose water. Pour into sterilized jars, and let cool completely. Store in refrigerator up to 6 months.
Love the flavor of this jelly! Made it twice, the first time it didn't set at all but the flavor was amazing I tried to reboil it to thicken but all I got was two less jars of my unset jelly as I had boiled it away. I made it again, thinking that the error was mine but the same thing happened when I tested it was still very thin. I added a second packet of pectin and that did the trick! Thick and delicious rose petal jelly!