From my experience, unless the cattleya is in a very open container (like slat basket or mounted), there is no need to mist the roots.
If you feel the urge to mist, just mist the leaves and avoid any water spills into the roots.
If the root's velamen is already saturated with water, it will not do any good giving it more water.

Cattleyas prefer a cycle of heavy drenching and dry periods. Constantly misting the roots prevents proper gas exchange in the velamen layer and encourages rot.
Just like light and dark periods are necessary for proper photosynthesis, so is a dry/wet period. The duration and intensity of the wet/dry period varies from plant to plant.