You don't need a Rogue. Anyone with high Dex will disarm traps and unlock things just fine (Ranger is easy to play as a high Dex class). You also don't need a Cleric. Anyone with a reasonable amount of Wis can detect them just fine (Ranger is a class that often has decent Wis)
As for a Tank, there's plenty of options to make a tank character. Including Wizard, Cleric, Druid, Ranger (Can go Beastmaster and use Bear too) in addition to the more straightforward Fighter and Barbarian.
In regards to doubling up on classes... It's not really that much of a problem. Each class has several ways to play it and multiclasses open up even more avenues for diversity.
