X axis following Y axis

If i have a roll of material and unrolling it with encoder installed on roller
how can synchronize this moving of material in one direction (Y axis) 
with X axis and Z axis to cut it for example with laser
Rollers have some speed adjustment  and accurate feedback for velocity position from encoder
but it is not like a real Y axis.

What controls the unrolling speed?

It is an analog potentiometer(inverter) 0-10v.
It is sheet coil unrolling machine that i want to cut
as unrolling happens.
Because y axis moves in one direction only it is not possible to do circular movements
or change direction but it does not needed in this case.

Or it is better to stop the unrolling read rollers encoder update material position and
put a regular Y axis like conventional plasma but with moving sheet material ?

Not sure but it seems simpler to have a standard X/Y plasma table
with a roll-fed extension. The roll feed could be implemented in hal,
perhaps using the limit component to generate the motion profile
with the required Y distance and a PID loop using the encoder as
feedback.

Can all this operation of unrolling to be transparent to gcode?
For example to have a gcode of cutting
diagonally a sheet of 10m.
plasma if y axis is 2.5m must start and stop
4 times.
Can this handled automatically without specific gcode?

Can roller with 0-10v inverter be V axis for example and unrolling handled in gcode?
Any better appproach?

For just a straight cut-off operation I think this is doable in hal.
(the unroll is done in hal, then the cut-off is just at the beginning of the Gcode)

If you want diagonal or other fancier cuts that gets trickier. I also expect that
the unroll operation would be less accurate than normal joint motions and
possibly unidirectional. It also needs to rehome when done.