With just a few different conditions, it seems like it's within the realm of possibility that ancient Roman technology could have been a nearly-sustainable peak of human technology.

What makes you think that? Technological growth had already hit a clear exponential curve by the time of Augustus. The large majority of the time to go from foraging to industry had already passed, and it doesn't look like our history was an unusually short one. Barring massive disasters, most other Earths must fall at least within an order of magnitude of variation from this case.

In any case, we're definitely at a point now where indefinite stagnation is not on the table... unless there's a serious regression or worse.