I'd never put rosies in a 10 gallon - realy too small for them and they should be in groups.
White clouds are nice (keep in mind that these and the rosies are
not tropicals). They have the added benefit of being very hardy and easy to breed.
Serpaes and rummies both need to be in groups. The 'rummies' will be smaller and therefore are better suited to a 10 gallon. Mind you, I'm going with the preassumption that the 'rummy noses' you see at most LFSs aren't rummies at all (true rummies,
Hemigrammus rhodostomus grow to 2" whereas the flameheads that most LFSs sell grow to 1.5"). If, however, your LFS actualy sells rummies, you'd be better off with the tetras since they are less active.
Note that the 'rummy noses' usualy sold at LFSs are
Hemigrammus bleheri. Look them up and make shure you can identify them. there are, in fact, 3 species sold udner the 'rummy' name. The true one is the only one with yellow in its tail. Both of the other two remain slightly smaller (max. 1.5").
If you were to ask me, I'd get spiketailed paradisefish (Pseudosphromenus dayi)

and maybe some pygmy cories and a small school of myer's hatchetfish.