There is a lot more to intersections and splines than making a material and adjusting a mesh…
You can probably start by creating a procedural mesh at the junction.
I would do so by calculating the angle splits between the several splines that intersect at the intersecrion point.
Each angle will become the starting tris that the intersection is based on.
There is almost no chance that the mesh will align with the end of the spline piece, so instead of attempting that, I would fake it by creating a piece of procedural mesh with more vertex at the joint.
Then I’d levarage a vertex shader to adjust the position of the vertex up/down to match the spline mesh (Distance to nearest surface or even distance field gradient).
Simply making sure the meshes (road and junction) can not cast a shadow is likely enough for most discrepancies to be overlooked by a player.
For your use case, i would probably also try and levarage RVT to output the meshes into a diffuse to then use as the unrelying paint for the mesh - this avoids or cures many visible issues and potentially also allows you to merge dofferntly colored bits of road when the intersecrion comes up.
Anyway, the hard part of playing with mesh generation/mesh sections is learning to think and model on a Tris By Tris basis.
I think intersections make a good jumping in point to learn over the fact their spline interesction point is alwyas the final tip of all the tris which will make up the road…
You can literally build pieces outwards from it and increase the complexity as you understand more of how to use the system…
Unfortunately, I don’t really see any good tutorials on the subject or I’d share.
The proc mesh compoent is often hijacked to do things like vehicle collision deformation, or shoot and change the object type stuff.