CBS has revealed that Rod Roddenberry (son of franchise creator Gene Roddenberry) and Trevor Roth (COO of Roddenberry Entertainment) has joined the upcoming Star Trek series as executive producers.
“Gene Roddenberry, the Great Bird of the Galaxy, left a finely feathered nest for all who love ‘Star Trek’ to enjoy,” said Fuller. “And it is only fitting that Rod Roddenberry and Roddenberry Entertainment join our new ‘Trek’ adventure to ensure that his father’s legacy of hope for the future and infinite diversity in infinite combinations runs through our tales as Gene Roddenberry intended.”
In general executive producers don't really handle the day to day decision making (that is what the showrunner is for). They do provide input on big picture stuff like budget, large story arcs, and lead casting but often even that is usually left to a single executive producer to avoid confusion and to foster relationship building with the network and various vendors (like FX companies) necessary to get the TV show made. My read on this is there is some legal obligation behind this additional and not much else.