Add this after you set up your main (`default) font. This line instructs Emacs to use the Comabria Math font (I hope it is standard with Windows) only for the delta symbol (defined at code point 120491), and keep the rest presented by the default font.
@zaeph recently updated Org-roam with this. Thank you for the quick change Zaeph; I didn’t think it was worth reporting as an issue (I even thought it might have been very minor with Windows fonts).
You can delete the line 27 that defines Cambria Math.
This previous line will be used to specify the font (Segoe UI Symbol). You can even remove it because Consolas can display the new delta symbol (I want to keep Segoe UI Symbol for other symbols though).
The new delta symbol looks like this with using the Consolas font: