Okay, here's what you really have to do. Give up on trying to make a heartline roll completely by hand. I tried it many many times, and even though I'm considered one of the best hand-builders on the site, I still can't do it. It's essentially impossible.
With that said, here is how you do it to generate a perfectly smooth roll, step by step.
1. Delete all the nodes that make up the interior of the heartline roll
2. Smooth the two end nodes out. You want a piece of track in the middle that is as close to straight as possible, and has smooth transitions into and out of it. Tip: The handles on both of the vertexes that define the segment should have handles that are approximately 1/3 the length of the straight segment.
3. Split the segment in half. Then split each half-segment in half again.
4. Make sure that each segment has Continuous Roll turned on.
5. If you're spinning clockwise, bank the first segment -90 degrees, the second one -180, and the third 90. If you're spinning counter-clockwise, use 90, 180, and -90.
6. Hit "select all", and delete every vertex except those used to define the roll and the segments directly before and behind the roll (makes reattaching easier).
7. Go to "coaster options" and change the main track color to pure black.
8. Save the element under a different file name.
9. Download the Automatic Heartline Generator, here:
http://www.coastercrazy.com/users/wws/NL-AHG_v1_6.zip
10. Boot it up, and hit 'load track' while selecting the file name of the shortened track element.
11. Use the following settings:
Segments: 25 (you need a lot of vertexes to get the shaping just right, but not too many since you need some leeway to be able to reattach it)
Heartline: 1.3, since it looks like an X-Car coaster. If it isn't, check the list on the right for the right value.
V In: 5
V Out: 15 (doesn't really matter since the track is all black.)
Precision: 10
Filter: 200 (we're using a very high filter number, because it will really smooth the roll out, getting rid of those annoying little bumps.)
11. Hit the "Heartline it!" button, and save the result under a new track name. (ver important... this lets you go back and change something if the AHG screws something up.)
12. Load the newly heartlined piece of track in the editor, hit "select all", then save it as an element
13. Go back to the original track, delete the old element, insert the new one, and voila! A perfectly smooth downward roll.