You can take as many classes as you want. The only limitation is the total levels (10) and alignment restrictions. A Paladin & Monk cannot be Barbarian and vice versa.
Also note that if you start as rouge (or anything else) and take a level as Paladin and then take levels OTHER than Paladin ( i.e Fighter) you CANNOT level up as Paladin again.
Same goes for Monk.
But you could build a Rouge2/fighter1/barbarinan1/cleric1/druid1/bard1/ranger1/wizard1/sorceror1 if you want.
BTW i love your party build, but your spellsword is flawed. A Brb1/wizard9 has BAB +5, +1 for Brb and +4 for wiz, same as a lvl 10 wizard (wiz 9 is +4, wiz 10 is +5) so there isn't much to gain by multiing your wizard.
And you wont be able to craft KEEN weapons, only a lvl 10 wizard/sorceror can do that. The sorceror only gets 2 lvl 4 spells so you shouldn't take the KEEN spell with him, since you also need the craft feat.
Hope this helps out
