Place the rhubarb, sugar, and 2 tablespoons water in a medium saucepan and bring to a boil. Reduce heat and simmer, stirring occasionally, until the rhubarb is tender and starts to fall apart, 10 to 12 minutes.
Remove from heat and stir in the strawberries, ginger, and coriander, if using. Let cool for 20 minutes.
Divide the ice cream among individual bowls and spoon the sauce over the top.