[Mr_J]

Well I'm a beginner but I'll give it a go.
First of all, obviously variance will be much higher playing the $100s with the much smaller edge.
I think that the $100s may take a little longer on average compared to the $10s because I think alot of players would be looser at lower limits (never played $100s, but it makes sense).

So, while ROI per sng might be higher for the $100, $/hr might be even after taking into account that you have a higher # of sngs per hour at the $11 table.

Also, w/ multi-tabling: I'd take a guess that if this affects your ROI, it has a larger affect the higher the level you play at. Ie, playing 8 at once at $100 will lower your ROI more than if you play 8 at once at a $10. I'm thinking this because opponents will make you think more at higher levels, and with 8 at once you probally don't get much time to think, so you may make more mistaktes??

"If someone has the normal goals of making as much as possible while not losing their bankroll,"

Depends on the size of the bankroll. However, you'd be able to use a much smaller BR (in terms of # of buy-ins) at the $10 sngs since variance is much lower there due to the much higher edge.

"Do you find the highest level in which you have a positive ROI?"

No. You'd find the level where you make the most $/hour.

"Does the lower ROI increase the ROR, or is this an incomplete problem without knowing the standard deviation?"

In this case yes, however a lower ROI doesn't always mean a higher ROR. You don't need to know the standard deviation, you can tell it's much higher at the $100s.