Hm.. I hope you corrected the roots more than you are showing. Right now you have all the makings of a 2-root nebari, the way I see it.
Young trees like this it is important to keep the nebari buried if you are trying to create a flat, radial spread of roots. Every time you repot, you must aggressively train the nebari, prune overly large roots off right at the trunk. All roots, all the way around, on trees this young, should be close to the same diameter, as the diameter differences will only become greater as time passes. Next year, remove those 2 fat roots right at the trunk when you repot. Then keep the entire nebari buried, at least 1/4 to 1/2 inch, so new, finer roots can sprout from the trunk to replace the fat ones you eliminated.
But it is a nice start.
The "normal or wild form" of linden has leaves that are quite large, and don't reduce as much as one might like. There is a cultivar, or a group of cultivars that are called "Little Leaf Linden", these are better for bonsai. The normal form, you should think "go large", a finished tree in the 3 foot tall range can be really impressive. As Shohin and small bonsai, the big leaves are always an issue.