A mounting system for a roller blind includes a tension bar for mounting under pressure between first and second sides of a windows frame. The tension bar may provide both long and short adjustment of mounting system width. The tension bar extends through a hollow roller tube of the roller blind, and through a clutch mechanism of the roller blind, and is coupled to end mounting fixtures. The length of the tension bar may be adjusted as a long adjustment of mounting width. Various mechanisms may be associated with one or both of the end mounting fixtures for short adjustment of mounting width, such as a latch mechanism, wedge mechanism, spring-loaded mechanism, or turn-buckle system. End pads at the ends of the blind provide friction and absorb excess pressure. The mounting mechanism serves as a universal window blind bracket and support rod, which requires no screws or nails to install.