You're missing the entire understructure of the roof. The tiles have to be laying on something! If you look up photos of old Japanese roofs, you'll quickly see that the roof has a noticeable thickness to it because of the protruding rafters, as well as a bunch of support brackets at each of the pillars.
Roof tiles in perspective, unfortunately, just require a bunch of work, there's no easy shortcut. Fortunately,
their structure is pretty simple, and they're not hard to draw once you get it. Overall, it's a series of spines (the narrower arched tiles) and troughs (the flatter, wider tiles). The higher tiles overlap the lower tiles, so from this angle (slightly from below) we'd see these sides of the tiles.
You've also got a massive tangent with the tree branch and the roof. Angling the branch more upward should fix that, as well as look more natural.
Here's a very sketchy edit to give you an idea of what the roof tiles and roof structure could look like: