It could use some pruning on the roots (shouldn't stretch that far out),
I've seen many trees with roots similar to that so I disagree that you NEED to trim their length.
Whats wrong though is they're all a little round at the end.
It would be ok if 1 or 2 of them were like that but we should be seeing the rest blend into the ground more.
You can also try to make at least 1 of the roots go in and back out of the ground.
With roots like that, we should also see some stronger definition of the forms blending into the trunk.
Start with some higher contrast blocking in of highlight, mid-tone and shadow (with optional backlight).
Try not to just do a line of the brightest pixels along the of those roots on the left, rather use a bit darker line and bring your highlight to the point that marks the highest point, since THAT is where the light would be most seen.
Vary how close your highlight is too the shadow (width of the mid-tone) to further define your forms.
You should feel comfortable with the forms based off these 3 shades only.
THEN tone down the contrast accordingly and start blending with some extra colours.
Again, you can vary how much blending you use to make the shapes more interesting, so some bits have a sharper edge and some are rounder.