there are many units that their attacks or mysteries, skip the opponent units def and/or res. i hope that i have answered your question about root of warrior passive.

Indra can cast his mystery 2 times in a round. this doesnt means that you can cast his myst one time first round and wait 2nd round to cast it again 2nd time.

if you cant cast his myst 2 times at same round the next round it will have his personal cooldown limit