A roof window arrangement comprising a plurality of window units (21, 22, 23) in a side-by-side configuration and a covering assembly including a set of coverings for each window unit, each window unit comprising at least one pane-carrying frame (211, 221, 231) and a pane (214, 224, 234), wherein at least one covering (512, 513, 5212, 5231) of a set of coverings associated to one window unit (22, 21, 23) is configured to function as a covering of that one window unit (22, 21, 23) and of a neighbouring window unit (21, 23, 22), and wherein at least one window unit (21, 23) of the roof window arrangement comprises a pane-carrying frame in the form of an openable sash (211, 231) which opens about a fixed hinge axis (α) defined by a set of hinges (212, 213, 232, 233), and wherein the set of coverings associated to each said at least one window unit (21, 23) comprises two side sash coverings (5211, 5212, 5231, 5232) to cover a lower portion of the sash (211, 213) from the hinges and downwards, and a separate bottom sash covering (5213, 5233), at least one of said side sash coverings (5211, 5212, 5231, 5232) being configured to function as a covering of a neighbouring window unit, wherein said plurality of window units comprises three window units (21, 22, 23) including a first window unit with a pane-carrying frame in the form of an openable sash with a top member, two side members, and a bottom member, a second window unit with a fixed pane-carrying frame with a top member, two side members (2212, 2213), and a bottom member, and a third window unit with a pane-carrying frame in the form of an openable sash with a top member, two side members, and a bottom member, such that the second window unit is positioned between the first window unit and the third window unit, wherein said fixed hinge axis is located between the top member and the bottom member of the frame, and wherein a common frame is provided to act as a single, stationary frame of all of the plurality of window units (21, 22, 23) in side-by-side configuration, said common frame being configured to be built into a roof surface and comprising a top member, two side members (12, 13) and a bottom member, wherein the covering assembly comprises a top casing and two side frame coverings (511, 514) connected to the common frame, and wherein the common frame is provided with two frame hinge parts (112, 113) for the openable window units (21, 23). wherein at least one covering (512, 513, 5212, 5231) of a set of coverings associated to one window unit (22, 21, 23) is configured to function as a covering of that one window unit (22, 21, 23) and of a neighbouring window unit (21, 23, 22), and wherein at least one window unit (21, 23) of the roof window arrangement comprises a pane-carrying frame in the form of an openable sash (211, 231) which opens about a fixed hinge axis (α) defined by a set of hinges (212, 213, 232, 233), and wherein the set of coverings associated to each said at least one window unit (21, 23) comprises two side sash coverings (5211, 5212, 5231, 5232) to cover a lower portion of the sash (211, 213) from the hinges and downwards, and a separate bottom sash covering (5213, 5233), at least one of said side sash coverings (5211, 5212, 5231, 5232) being configured to function as a covering of a neighbouring window unit, wherein said plurality of window units comprises three window units (21, 22, 23) including a first window unit with a pane-carrying frame in the form of an openable sash with a top member, two side members, and a bottom member, a second window unit with a fixed pane-carrying frame with a top member, two side members (2212, 2213), and a bottom member, and a third window unit with a pane-carrying frame in the form of an openable sash with a top member, two side members, and a bottom member, such that the second window unit is positioned between the first window unit and the third window unit, wherein said fixed hinge axis is located between the top member and the bottom member of the frame, and wherein a common frame is provided to act as a single, stationary frame of all of the plurality of window units (21, 22, 23) in side-by-side configuration, said common frame being configured to be built into a roof surface and comprising a top member, two side members (12, 13) and a bottom member, wherein the covering assembly comprises a top casing and two side frame coverings (511, 514) connected to the common frame, and wherein the common frame is provided with two frame hinge parts (112, 113) for the openable window units (21, 23).