Roller blinds are an excellent window covering, especially in small spaces where they look better than curtains. For maximum blackout light control you can pair roller shades with curtains, which help block light around the edges. Despite their utility, roller blinds are extremely simple compared to other blinds. It basically consists of a sheet of fabric of the same proportions of the window frame, but slightly smaller so it will fit. The length is a little longer than the window to make up for the connective area at the roller frame and the hem along the bottom.
You can make your own roller blinds by using kits from hardware stores and DIY websites. However you can also convert your old roller blinds to a new material easily without anything but the new material and a way to attach it. If you are using your own fabric, the best bet is a stiffer fabric that has been treated to be water resistant. Roller shades are not recommended to be used outside the home, but windows can be a very wet place.
Fabric is inexpensive and can be found in a variety of sizes so make sure you pick one that fits first, instead of trying to join two different pieces of fabric together. That is, unless you are an artist and want to make your own fabric patterns. Custom made fabric roller blinds are starting to become popular among the hip and handy community. Stiffened fabric is very easy to work with because you can cut it against the grain.
Hardware stores also sell stiffening solution that you can apply to the material of your choice. Stiffer roller blind fabric is less likely to bunch up or jam because it rolls up very neatly. Stiffened fabric is also frays less easily. I still recommend seaming the edges for lightweight material to keep it from fraying. If you are really artsy you can do things like lace, cut out designs and tassels to make your roller shades a little less boring. Use PVA glue to stiffen the fabric if you cannot find the stiffener yourself, but be careful of the warnings.
The spring-loaded roller mechanism is the one piece you won’t be able to make yourself. Most kits come with double sided tape to attach the material to the roller at the top. If not, you can use tacks or staples to connect it directly to the roller. When correctly installed, the blinds should roll up with a simple tug.