Use roles without inventing classes
GRAIN ROT is built for one to four players, but that does not require rigid class labels. Assign temporary jobs around the objective: lead navigation, watch the rear, handle priority loot, or manage the retreat call.
Roles can change after a loss or important pickup. What matters is that the crew knows who is doing each job now.

Keep callouts short
Use names or agreed labels for threats, direction, priority loot, regroup, and retreat. A long explanation during contact is usually late.
Repeat the extraction call and wait for acknowledgement. The developer FAQ's team-loss warning makes a split retreat especially costly.
Resolve disagreement before moving
When one player wants another room and another wants to leave, stop in a defensible space and compare the pre-run exit rule. Do not let the fastest player decide by walking away.
A crew that extracts together can debate the risk at the Outpost. A crew that splits often returns with neither the loot nor a useful lesson.

Sources
Official GRAIN ROT Steam store page →