If you'd like to see your own genres in Roon, simply visit the Library tab of Settings, then, edit your Import Settings. You might choose to enable both options, or to totally opt-out of Roon's genre assignments and do it yourself.
Roon supports full editing of genres, and genre assignments. Don’t like that Daniel Barenboim is tagged as “Latin”? By all means, remove it.
Roon also supports the editing of the genre hierarchy itself. Is Tango a Top-Level genre for you? By all means, put it at the Top-Level. To edit a genre, or to add or remove genres from an album or artist, just click Edit (from the 3 dots menu) on the album or artist page, or the Pencil on the genre page.
Roon supports mapping genres extracted from your file tags when they’re brought into Roon. This mapping allows you to:
Re-write genre names. This is common for near misses like “Prog Rock” vs “Progressive Rock” or “Post Bop” vs “Post-Bop”
Hide genres that you don’t want to see in Roon
Genre mappings are accessible only if you have "Use genres extracted from file tags" set to Yes. You can access genre mappings in Settings > Library > Genre Mappings.