Having made many different kinds of fruit jellies and jams, I have to admit to never having made your described recipe. I make an excellent apple jelly that doesn't use pectin. The catch is to ues fruits with naturally high content of pectin, such as the apples. So, I'm assuming you use some kind of fruit juice with the rose petals, so perhaps this will work for you. The sugar/apple juice is cooked at a slow roiling temperature with almost constant stirring to prevent sticking and scorching until reaching the sheeting stage. Here, you take a cool metal or wooden spoon and dip it into the mixture and hold it up over the pan to observe a sheeting or slow "folding" action of the mixture from the spoon. It's difficult to draw an adequate word picture but once you see the correct stage you'll always know it. When it reaches this stage, place it in the sterilized jars and seal according to the instructions for canning. Works well for me... Luck!