In a medium-sized saucepan, bring the water to a gentle boil. Gradually add the sugar, stirring until it has fully dissolved.
Add the rose petals, grated apple, and lemon juice to the pan.
Stir occasionally and cook the jam gently over medium-low heat. You want the apples and rose petals to soften and become tender, and for the syrup to thicken lightly, about 30 to 40 minutes.
Once the apples and petals are soft and a light syrup has formed, remove the pan from the heat. If you’d like a smoother texture, you can blend the jam a bit, or leave it as is for a more rustic, chunky texture.
Pour the hot jam into clean, sterilized jars. Let them cool at room temperature before refrigerating. This jam will keep for about a month in the refrigerator.