Hi Requios,
There is not currently a way to set the roll of a spline point, however we have a feature request in our system to improve upon spline manipulation over time.
Right now, you can set the rotation of the Spline Mesh Component that makes up the track. You can do this within blueprints and code. Basically you will need to get the tangent and distance of the spline and using math, calculate the correct rotation of the Spline Mesh Component.
Cheers,
TJ