Chop the rhubarb into short lengths. Toss with the sugar and rosewater and spread out on a tray. Cover with foil and place in the oven for 10 minutes.
Remove the foil from the rhubarb and return to the oven for a further 5 minutes until tender and the juices are syrupy. Leave to cool.
Puree half of the roasted rhubarb - you should have about 1/2 cup. Whisk together the rhubarb, coconut cream, sugar and rosewater until well combined. Place in the freezer to chill for up to an hour whilst you prepare the chocolate layer.
Melt the chocolate over a pan of gently simmering water.
Whisk together the chocolate, coconut cream, cocoa powder and a pinch of salt, if liked.
Place into the freezer for 20 minutes until the mixture has set. Whip using a stand mixer or hand mixer until light and fluffy.
Pour the chocolate mixture into a freezer bag, snip off the corner and use as a makeshift piping bag to decant the mixture into serving glasses.
Place a couple of pieces of rhubarb on top of the chocolate layer and then pour the rhubarb mixture over the top. Finish with some more roasted rhubarb, chocolate shavings and a few rose petals if you want to make them extra pretty.
Refrigerate for at least 4 hours before serving.
The rhubarb mixture won't set up as much as the chocolate mixture, but it has a lovely soft consistency which sits perfectly on top.