Comma positioning between title and name and conjunction

As the inclusion of the position titles is not necessary to determine which individuals are intended by the references, I would suggest that treating them as descriptive clauses would be the appropriate choice:

Rmt, LLC will be managed by Sally Red, CEO, and Sean Brown, COO.

I would also suggest that CEO is not a title in the narrow sense, such as President or Judge. Also notice it is not a degree, such Ph.D. All of these qualifications express achievement that is retained throughout life and preserved across contexts.

The titles in your example apply only in the context of a specific company and only as long as a named individual holds the position.

The more verbose construction of the same statement would be:

Rmt, LLC will be managed by Sally Red, who will be the CEO, and Sean Brown, who will be the COO.

This form is not necessary, only useful to illustrate the choice.