`org-roam-mode` based buffers use `magit-section` to render sections.
The problem is that `magit-section` will layer keymaps for each section
under a text property. In Emacs, text property based keymaps have a
higher precedence for a lookup[0] than `emulation-mode-map-alists`, in
which Evil and leader keymaps are stored in.
[0]: https://www.gnu.org/software/emacs/manual/html_node/elisp/Searching-Keymaps.html