As a ranger you can get Sleight of Hand and don't need an extra rogue for that. I think it comes with Urban Tracker.
You can go with two wizards, a fighter and a walrock easypeasy - or any other combo. Most classes have something to help them - wizards have the Knock spell for example, fighters can just trash a locked chests...
And you don't always need a cleric. Granted, Shadowheart hasa lot going on storywise, but you don't need to have her always in your party. A druid has healing spells too, paladins and rangers get them too.
And if you really need a different role, you can normally go to camp from most, bu ta few places
