You can set the stem direction of any selected notes
(provided they are a sort that have stems) using the three
Stem Direction options on the Notes menu. The options allow
you to either fix the stems up or down, or revert to the stem
direction that Rosegarden would otherwise have chosen. See
also Beams.
The Notes menu also contains options for adding slashes
across note stems, for example to indicate short repeated
notes or drum rolls. These are currently purely notational;
Rosegarden will not take them into account when playing the
staff or generating MIDI.