A roof assembly for a vehicle, comprising a vehicular roof provided with a light admitting portion and a sunshade assembly carried by said vehicular roof, the sunshade assembly comprising: • a guide device fixed with respect to said vehicular roof; • a deployable shade device comprising a sliding support coupled to said guide device in a sliding manner along a first direction and a first sun visor having an end carried by said sliding support and being extensible, so as to be configurable, in reply to a corresponding sliding of said sliding support, between a retracted configuration and a deployed configuration, in which respectively reaches a smaller and a larger extension; • restraining means (26, 11, 30) configured to cooperate in contact with said deployable shade device to keep said first sun visor in the deployed configuration, in which said first sun visor covers said light admitting portion; and • a locking seat adjoined to an end portion of said guide device, so as to receive said sliding support when said first sun visor is in the deployed configuration; said assembly is characterized in that said sliding support is movable within said locking seat between an incoming position, in which said sliding support is aligned with said guide device to engage therewith, and a locking position, in which said deployable shade device cooperates in contact with said restraining means (26, 11, 30), such that said sliding support is prevented from escaping from said locking seat; and wherein said restraining means (26, 11, 30) comprises releasable locking means configured to exert a locking action onto said sliding support when in the locking position to prevent said locking position to move toward the incoming position and wherein said locking means comprises at least one engagement member fixed with respect to said roof, engaging in a releasable manner with said sliding support while in the locking position, and configured at least to limit mobility of said sliding support when engaged therewith. • a guide device fixed with respect to said vehicular roof; • a deployable shade device comprising a sliding support coupled to said guide device in a sliding manner along a first direction and a first sun visor having an end carried by said sliding support and being extensible, so as to be configurable, in reply to a corresponding sliding of said sliding support, between a retracted configuration and a deployed configuration, in which respectively reaches a smaller and a larger extension; • restraining means (26, 11, 30) configured to cooperate in contact with said deployable shade device to keep said first sun visor in the deployed configuration, in which said first sun visor covers said light admitting portion; and • a locking seat adjoined to an end portion of said guide device, so as to receive said sliding support when said first sun visor is in the deployed configuration; said assembly is characterized in that said sliding support is movable within said locking seat between an incoming position, in which said sliding support is aligned with said guide device to engage therewith, and a locking position, in which said deployable shade device cooperates in contact with said restraining means (26, 11, 30), such that said sliding support is prevented from escaping from said locking seat; and wherein said restraining means (26, 11, 30) comprises releasable locking means configured to exert a locking action onto said sliding support when in the locking position to prevent said locking position to move toward the incoming position and wherein said locking means comprises at least one engagement member fixed with respect to said roof, engaging in a releasable manner with said sliding support while in the locking position, and configured at least to limit mobility of said sliding support when engaged therewith.