How can i make a roller blind from some material?

How can i make a roller blind from some material?

i have some gorgeous fabric i bought to make curtains for my daughters bedroom, but there isn't quite enough. I would like to make it into a blind instead, how would i do it? is there something i can put in between the front and back layers to make it a blackout blind? or at least block out some light as the fabric is very thin. I already made curtains from it, but they are about 2 cms to short and look a bit silly – but they will be long enough to make the blind from as the curtain pole is about 6″ above the window frame. if i need to buy a kit i'm in the UK