You only really need those two. If you fly a lot, then yes, it's worth it. The throttle is great, though it won't actually help you control roll (well, it has a thumbstick, but it'd be awkward for that). It is a bit simple (no detents, moves in a straight line) and the thumbstick may need a deadzone (though maybe it's just my throttle that has the centering spring worn out), but it's very ergonomic and pleasant to use. Pedals also have 3 axes, so they can be used for driving games as well (at least if you don't need a clutch pedal).
Both pedals and throttle are certainly worth the price. Once you get used to a HOTAS setup, it's hard to go back to anything less.
Immersion is amazing and flying feels very natural, especially in flight sims.