A similar approach can be taken in Photoshop, but here is one solution done in Illustrator:
1) Draw rectangle
rectangle > Effect > Stylize > Rounded Corners > ~10px
3) Select Direction Arrow (a) > Grab top right corner of rectangle holding shift
to keep structure and create your desired angle
rectangle > Object > Expand Appearance --This will make the stylized rounded corners actual points that will be used for the outline
5) Duplicate this
rectangle(cmd+copy, cmd+f to paste in front)
> Object > Transform > Reflect > Horizontal -- set aside for now.
6) Draw new rectangle
7) Place new rectangle over original rounded corner rectangle, aligning baseline of both rectangles
8) Select both
rectangles > Pathfinder > Minus Back -- (ignore 2nd rectangle on top, shouldn't have included it in this screenshot)
9) Align 2nd rounded rectangle to baseline edge.
all > Pathfinder > Divide -- This will allow you to delete the excess area
Select all > Pathfinder > Merge
Obviously, this is not the best solution for everyone, but it should help you wrap your head around at least one way to achieve this result. I often just need someone to get me started down a path to a solution. Hopefully this does that for you.