do you think its ok to root pcb tracks under this sepic inductor?
(i.e. go between the pads on the same side of the board as the inductor is mounted on.)
-or wll the track be shorted by the underside of the inductor?
Not recommended at all.. you should not run tracks below few things....
1. Inductors
2. Power transistors
3. Regulators (SMD)
4. Crystal oscliiators etc
Notice that the ferrit body is conductive so the voltage applied between the coil of the inductor and the track under the inductor will be applied on the insulation of the inductor wire and the solder mask. The solder mask thickness can vary but it's usually thinner on narrow tracks (due to cappiliar effects). The wire insulation is also quite thin and can't widstand big voltages. Like result if the track is under the inductor it becomes critical the voltage between this track and the inductor wire
normally you should not do this. But if you can consult with the circuit designer and you are absolutely sure that the voltages involved are within safe limits, then it can be a case-to-case basis.