Wash the strawberries and rhubarb well. Hull the berries and dice them into small pieces. Chop the rhubarb into segments approximately 1/2 inch in size.
Place the chopped fruit in a glass or ceramic bowl and cover with sugar. Stir to combine and cover. Let the fruit sit for at least an hour, until the juices are flowing. I often pop the bowl into the refrigerator at this point and cook the jam the following day.
When you're ready to cook the jam, prepare a small boiling water bath canner and three half pint jars and bring it to a boil. Place three new canning jar lids in a small pot and bring them to a bare simmer.
Pour the fruit and all the liquid into your jam pot and place it over high heat. For these small batches, I like to use a 12-inch, stainless steel skillet, but any low, wide, non-reactive pan will do.
Bring the fruit to a rapid boil and stir regularly. Over high heat, this jam should take 8 to 12 minutes to cook. It is done when it is quite thick. You can tell that it's ready when you draw your spoon or spatula through the jam, and it doesn't immediately rush in to fill that space. It will also make a vigorous sizzling noise when stirred when it is finished.
When the jam appears to be finished, stir in the rose flower water. Stir until it is incorporated and cook for an additional 30 seconds. The flower water is added at this point so you don't evaporate all the fragrance during cooking.
Remove the jam from the heat and funnel it into the prepared jars. Wipe rims, apply lids and rings, and process in a boiling water bath canner for 10 minutes (start your timer when the water returns to a boil, not the moment the jars go into the water bath).
When time is up, remove jars from canner and set them to cool on a folded kitchen towel. When they are cool enough to handle, remove the rings and test the seals by grasping the edges of the lid and lifting the jar an inch or so from the countertop. If the lid holds fast, the jars are sealed. Any unsealed jars should be refrigerated and eaten promptly.