What is the connection between the piston and connecting rod? I see a pin through the piston. If you have rotational freedom of the connecting rod to the piston at that pin, that would be a mistake.

The link with the slot in a Scotch yoke mechanism must have only translational freedom and all other DOF must be constrained.

If the piston, pin and connecting rod are bonded together, you could add a Translational Joint to ground on the Piston so that it can only travel along the Global Y axis.

The disk would have a Revolute Joint to ground.

Use Frictional or Frictionless Contact between the slot faces and the roller. 

It doesn’t matter that there is an edge on the roller face, but if you open the geometry in SpaceClaim, on the Repair tab, click Extra Edges and it will delete that edge.