Rosegarden supports playback of ornaments using its triggered segments mechanism. You can create triggered segments containing any of the various types of trill or ornament you might want, and associate them with the notes that want to play them.
To create a new type of ornament, first write out the notes "in longhand" that you want the ornament to play, and then select the notes and use ->->. This cuts the notes to the clipboard, pastes them into a new triggered segment, and replaces them with a single note of the same duration that triggers this segment.
To make a note play an existing ornament, select it and use ->->.
To edit the notes played in a triggered ornament, you can double-click on the note that triggers it. This will change all uses of that ornament, not just the one that you double-clicked on.
Note that while Rosegarden can shift triggered segments up and down in pitch to match their triggering notes, it is not clever enough to perform transposition into a different key or scale position.
See triggered segments for more details about ornaments and other uses of triggered segments.