Here is a sketch of a simply supported beam, with a pinned end and a roller end.

This is very different from a fixed end and a roller end.

With a center load, the shape of the deformation for a fixed-roller is very different to a pinned-roller beam. Do you see that the tangent to the beam at the left end has a zero angle, while for the pinned-roller case, there is a non-zero tangent angle on the left end of the beam.


What end conditions do you really want on your beam: Fixed or Pinned (simply supported)?

 I think you want a Pinned left end, even though you are saying Fixed.