Activate all mana-producing nonland permanents you control by tapping them, adding at least {3}{U}{R}.
Cast Dramatic Reversal by paying {1}{U}.
Activate Rootha by paying {2} and returning it to your hand, copying Dramatic Reversal.
Resolve the Dramatic Reversal copy, untapping all nonland permanents you control.
Activate all mana-producing nonland permanents you control by tapping them, adding at least {3}{U}{R}.
Cast Rootha by paying {1}{U}{R}.
Repeat from step 3.
If nonland permanents you control can tap to produce at least {4}{U}{R}, this combo nets infinite mana.

Infinite ETB

Infinite LTB

Infinite magecraft triggers

Infinite mana nonland permanents you control can produce

Infinite storm count

Infinite untap of nonland permanents you control

Rootha, Mercurial Artist

Dramatic Reversal

Prophet of Kruphix

Activate all mana-producing lands you control by tapping them, adding at least {4}{U}{R}.
Cast Turnabout by paying {2}{U}{U}.
Holding priority, activate Rootha by paying {2} and returning it from the battlefield to your hand, copying Turnabout.
Resolve the copy of Turnabout, untapping all lands you control.
Activate all mana-producing lands you control by tapping them, adding at least {4}{U}{R}.
Cast Rootha by paying {1}{U}{R}.
Repeat from step 3.

Infinite mana lands you control can produce

Infinite untap of lands you control

Turnabout

Combos with "Prophet of Kruphix"