UK roundabouts enter at a tangent. That's a main point of their design, altering the angle of potential collisions, sometimes to the point of reducing visibility to force people to slow down. The curve also should slow people down.
Some roundabouts (most of them in my region, Sophia Antipolis, Ftance) are designed with a tilt to the outside, so that the car would be ejected if it takes them too fast.
Roundabouts are a UK invention, fwiw.