Does Roon play Tidal in the same quality as the Tidal player itself?

Yes it does, except The TIDAL player app does not support bit-perfect modes to your audio outputs. Are you using bit-perfect modes (exclusive mode) in Roon? That could explain the difference.

If you click the little light next to the now playing track title in the footer of the app, you will see exactly what is being played and how.

if you are seeing TIDAL tracks that are not lossless in Roon, then there are 2 possibilities:

  1. the TIDAL account is not a tidal hifi account, but only the $10/mo lossy account
  2. TIDAL is returning us a lossy stream even though we asked for lossless – sometimes the labels give them lossy data, and they are working on fixing those