RE: Creating Roundabout

Within the file you submitted, I'm able to create a civil cell from it. But after I've done so, I see that there are a ton of elements that aren't collected into the civil cell. I guess some of those are for another attempt at a civil cell, but there are a few that seem to belong to the main one.

Otherwise, it seems to behave well. When I move the baselines around, everything seems to work, except if the angle is too acute or obtuse. In such a case, some of the arcs break.

I see that RdEOP83 and other similar arcs have an end point located by intersection. What is this intersection? Unless this intersection is established by Civil elements (and it looks like it must, since I'm not seeing anything else that would establish the intersection), I would recommend instead of using an intersection, use a 2-center fillet:

Use the 2 Center Arc tool. Since your 26-m-radius arcs are 6 meters long (but extended from there), you might use a Curve back transition with a 26-m radius and 6-m length, and the primary fillet would have a radius of 12 m. That might be a little cleaner anyway, and from a quick test, these arcs are more responsive.

I don't know that this will solve your problem, but I think it will be an important part of your solution.