Not 10, I can assure you of that. And I very much doubt you'd need 4, which would be the equivalent wattage of 10 2" downlighters with CFLs in.I'm not sure how many you would need to be bright enough for a kitchen.
Which shows, I hope, what is wrong with those little lights - they are not designed to provide general whole-room illumination, and they do a poor job of it. For any equivalent lamp type, incandescent, CFL, LED, you'll need a greater wattage of 2" recessed downlighters than if you use a light fitting designed to light rooms up.
Also, hardtail, using those lights is going to create a number of other problems.
1) You'll have to make holes in the insulation, which will make it less effective, which is a contravention of Part L of the Building Regulations.
2) As it's a flat roof you won't be able to seal the holes you make, and given that it's a kitchen you'll get warm moist air getting into the roof space where it will cause condensation problems, and that's a contravention of Part C.
Installing these lights is notifiable, so the above contraventions can't be ignored.
Even if you plan to ignore them, along with the requirement to notify, will you be able to ignore the dirty marks on the ceiling from airborne particles carried by convection currents and the rotting of your roof timbers? And all so that you can have lights which don't work?
