Wiring in a bath heater,vent, fan combo with power source coming from ceiling
If you were using separate switches:

Use the two wire cable to switch device #1. Use the white as the hot and mark it with black tape or marker. Use the black as the switched feed back to the ceiling box.

Use the three wire cable to power the other two devices. Use the white as the hot and mark it with black tape or marker. Use the black as the return switched hot for device #2 and the red as the return for device #3.

At the ceiling box, attach the incoming hot to the two white wires going to the switch box. Mark both of those whites with black tape or marker. Attach black and red wires from the switches to their respective devices.

Also in the ceiling box, attach the white (neutral) from the feed cable to the white on each device.

Attach all ground wires (green or bare) to all other grounds in each box.

If you re using one switch with a common hot:

Mark both white wires in the switch box with black tape or marker. Attach them together with a pigtail (a short length of wire). Attach the pigtail to the common terminal on the switch. Use the black wire from the two wire cable to one of the three other terminals. This will switch device #1.

Use the black from three wire cable as the return switched hot for device #2 and the red as the return for device #3.

At the ceiling box, attach the incoming hot to the two white wires going to the switch box. Mark both of those whites with black tape or marker. Attach black and red wires from the switches to their respective devices.

Also in the ceiling box, attach the white (neutral) from the feed cable to the white on each device.

Attach all ground wires (green or bare) to all other grounds in each box.

[Note: This may seem a bit strange since you are running parallel hot wires and attaching them to each other at both ends of the run.  This is done to comply with the rule that a circuit must be complete within each cable, to avoid possible induction heating.]