To a medium saucepan set over medium heat, add water and bring to a boil. Add rose petals and sugar; stir until sugar has dissolved. Reduce the heat and simmer for 20 minutes.

Whisk in pectin; increase the heat and boil, while whisking constantly, for 1 minute. Remove from heat and stir in lemon juice. Using a small ladle or spoon, skim off any foam from top of jam.

Pour into individual jars or a shallow baking dish for jam to set. Transfer the jam to a piping bag fitted with a medium plain round pastry tip.

Pipe a cherry-size portion of jam into the center of the flat side of a cooled macaron. Place another cookie, flat side down, over the filling and gently press just enough to push the filling out towards the edges. Once filled, macarons can be refrigerated in an airtight container up to 3 days.