Wait a week and see if the wall cures to the same depth of color as the brushed area. Different paints dry differently, depending on temp and humidity and brand of paint as well. If, after a week, you still see a really noticeable difference, the only thing I can think of would be to re-roll the wall area, skipping the parts where you cut with the brush. That might catch it up. Hope you don't have to do that, though.

I have just painted my dinning area with magnolia emulsion, since it has dried the edges and corners that I painted with a brush have dried out a considerably darker in colour than the rest where I used a roller. I don't think I used too much paint around the edges etc but am aware that the brush texture is slightly different that the roller.

Has anyone any suggestion as to how I can fix this or what I am possibly doing wrong?

Thanks!!