Depends a little on how & how many pieces you're doing.......for a bit of char on the corn, above is a great way to go.....I usually don't get to 'case the wife gets to it & wraps w/ butter & spices most always.........that way, 30~ min. 300+ roll a few times, near, but not right over coals......
Taters, if say medium Yukons which I like, oil, S & P, garlic powder, wrap.......down in NEAR or even on the coals (depends on if you want to tangle with pulling the grate aways in to rotate), maybe 45~1 hr. if a decent size coal pack.....a bit longer if it's larger taters, if they're huge bakers, might be as long as 2 hours...........
I checked one time, when I knew they were about the way we like them, and got 210f temp, pretty fluffy at that point, if you like a bit of chunkiness, go less.........
If it's just a few pieces, like so maybe:
If more, maybe spread out the taters across the grate & use coals on both sides?
The more stuff, the more creative the setups.......