$\triangle OIM$ is isosceles, $\angle IOM = \angle IMO$
Also since $TM \parallel OR$, from opposite interior angles, $\angle ROM = \angle IMO$,
From here you have the result.
$\triangle OIM$ is isosceles, $\angle IOM = \angle IMO$
Also since $TM \parallel OR$, from opposite interior angles, $\angle ROM = \angle IMO$,
From here you have the result.