GM as player, dice rolls?

Because we lost a player last minute I am controlling a character in our Starfinder game.

I notice my default my GM dice rolls are hidden from the players.

I'd like my character rolls to not be, but I'm assuming there is no way to say roll M hidden, roll character visible?

No. GM rolls are either on or off. You can't set some rolls on and some off.

Get one of the players to control the other character rather than you controlling it.

the only option you have is to set Show GM rolls to on and set the Dice Tower to on. Then all rolls will be shown, except the ones you drag to the dice tower. It's probably too much of a hassle to drag/drop all NPC rolls to the tower though.

The best option, imho, for you would be to run another instance of FG as a client, join your game (localhost server) and run the character from there...