Reefing down is an act undertaken explicitly by the lights of the skipper. Some will deep-reef when 25 knots arrives. Others at 40. There are no rules other than the skipper and crews physical and emotional comfort.
Having said that an averagely well designed boat can hold full-sail in 25Knots, gutsing 30/25, when a crew is available for good trimming through the gusts. Short-handed, or a skipper with an inexperienced crew would probably do well to reef earlier.
Up to around 30/35 knots gusting, if the skipper is competent and knows his boat, then roller reefing 'is' an option. But remember, your full headsail is a light-weight sail designed for modest conditions.
Further, if your boat is a bit tender then as you roller-reef you step the centre of effort higher and higher, which can increase heel angle.
In truth, if you have roller reefing on a 120/130% headsail it would be better to buy a much smaller, much heavier haedsail with a wire luff, and fit a snap ring into your foredeck and use your spinnaker halyard as the hoist.
Make sure you buy such a sail where the clew is in the same line of attack as your main headsail's. That way you can simply unclip the big one and clip on the small. Furthermore, in doing this, the cenre of effort is kept as low as possible.
Hope that hemps.