There's something bothering me but I can't put my finger on it. But I'll try...
The problem I have is at either side. The tree appears to have two "hands" hanging on for grim death to the banks. That's understandable. So, what's wrong?
I think there are two connected problems, but mainly because I can read this in two ways.
The right-hand side is clearer, so I'll concentrate on that. The roots divide and divide again into ever smaller roots but...
Are they entering the ground?
Or...
Are they hanging in space because the ground has fallen away?
I can't tell.
And if they're growing into the ground, what is that ground? Is it closely cropped grass? Or maybe smooth rock?
And, whether rock or grass, is it vertical? Or is it sloping towards us?
I think you're telling an interesting story but omitting some of the information that we need to understand it fully. Or, maybe you drew from a reference without working out what you were seeing?
I must say at this point that the tree itself works wonderfully well. It's just the two sides that trouble me.
According to the tree, the light is shining from the left and slightly forward of it. But other parts don't conform to that, so you lost depth. For example, the roots over the cave to the right of the tree, when I look closely, overlap each other. But none appear to be casting shadows on those behind, so the overall appearance is flat. The same applies to the roots at the left. Remember, you're telling a story - don't concern yourself with what the reference looks like, interpret it so you tell your story clearly. I'm resisting the urge to play with your drawing... so far successfully
...but I'm still troubled. If the rocks are rocks... what is the tree feeding on? And if the "rocks" are grassy mounds...?
OK, my curiosity got the better of me and now I know what it's on... I couldn't find a photo from exactly the same angle as yours - but it's close. It's clinging to a sandstone cliff at the back of a beach. Some roots are hanging in the air. Others grow into the thin soil on either side.
So, all that's missing from your story are the shadows within the roots and cliff. Personally, I think this would benefit overall from much stronger darks. That would give more contrast, and values to work with. And then I'd want to play with those roots and create three-dimensional depth - including shadows (and texture) within the cliff face. Not to the extent that it would dominate the tree, but to add more to the story being told.
But don't let my preferences take anything away from your drawing. It's a fascinating subject, and a lovely, well-drawn tree.