The present disclosure provides hydrosilylation curable compositions comprising resin linear organosiloxane block copolymers comprising, among other things, from about 0.5 to about 5 mole % C1 to C30 hydrocarbyl group comprising at least one aliphatic unsaturated bond. Such hydrosilylation curable resin-linear organosiloxane block copolymers have significantly faster cure speed, relative to their condensation curable counterparts. A faster cure speed can be important for encapsulating electronic devices, such as light-emitting diode (LED) chip devices, particularly devices having tall structures.