Do you need special recessed LED housing for angled / sloping ceilings?
A housing can either take a bulb or a retrofit LED ring that sits on the end.  If you use a bulb (LED or otherwise) then the angled housing can be of benefit, by keeping the beam pointed in the downward direction.  However if you're using a flat LED ring, there's no benefit to using an angled housing, because it's going to sit on the slope anyhow.

If you're concerned about lighting the area in a downward fashion, you can either use an angled housing:



with a LED bulb in it:



or use a standard housing:



with what's called a "gimbal" fixture.  A gimbal fixture looks like this:



And will allow you to compensate for the slope in the ceiling, by pivoting the fixture inside the housing.