Preheat oven to 180C/350F
Chop the rhubarb stalks roughly into 1 - 2cm lengths.
Lay them in a single layer in a roasting tin, sprinkle with a little sugar and cover with aluminium foil.
Roast for 10 - 15 minutes or until softened.
Remove the aluminium foil and roast for a further 5 minutes. Leave to cool.
While the rhubarb is cooling, peel and core the apples and slice them into chunks.
Lay a tea towel on a baking tray and place the apple slices on top. Cover with another tea towel.
Place the flour and spices into a large bowl and toss your apple pieces until each one has a light coating. Remove apples and put to one side.
Toss the cooled rhubarb in the remaining flour mixture.
Lightly grease a 20cm/8 inch pie plate.
On a lightly floured surface roll one disc out into a circle large enough to fit your pie dish with a slight overlap. Place in the prepared pie plate.
Roll the second disc out until large enough to cover the top of your pie.