The epiphytic Tillandsia absorb water and nutrients from the trichomes on their leaves. The roots are produced to only essentially anchor the plant to the branches onto which it grows in nature.
Most Tillandsia are purchased/ shipped without any sign of roots.
Here is a native Florida Tillandsia recurvata naturally firmley attached to a branch.
Here is a look at it after careful removal from the branch showing the brown thread like anchoring roots.