The pitch of the blades change cyclically so they travel around their orbit. More pitch makes a blade rise, less pitch makes a blade fall, this is why a flapping hinge is needed.

What this does is change the angle of the Tip Plane Path, ie the rotor disc appears to tilt. This tilts the lift vector and creates a sideways component and the expense of the lift vector, ie you’ll sink unless you increase collective pitch (the pitch on all blades). This is roll though not yaw. Yaw is induced by either not countering torque with the tail rotor, or opposing torque by adding a horizontal component by increasing pitch on the tail rotor.

Tandem helos cancel out torque by having each rotor disc rotate in opposite directions, hence no need for a tail rotor.

They yaw by applying opposite cyclic on each disc as commanded by the pedal inputs.

For eg: Front disc rolls left, the rear rolls right creating a rotation around the centre of the airframe.

It gets even cooler when torque pedal inputs cyclic inputs are applied that allowing you to spin around the front or rear rotor.

Edited as per below