Romania's rovinieta: what it is and how it differs from a vignette
Why a vignette from a neighboring country won't get you anywhere in Romania.
Most of the countries in central Europe run some version of the same idea — pay in advance for road use, checked against your plate. Romania does something similar but calls it a rovinieta, and it's worth understanding that it's a genuinely separate system rather than just a different name for the same thing.

The practical effect is that a vignette bought for Hungary, Slovakia, or Austria won't get you anywhere in Romania, and a rovinieta doesn't cover you once you cross back out. If your route runs through several of these countries — which is common on longer road trips through the region — you end up buying a separate pass for each one, on each country's own terms and through each country's own system.
This catches people out more often on multi-country trips than single-destination ones, since it's easy to buy one pass and assume it travels with you. It doesn't. Budgeting for the rovinieta as its own line item, rather than assuming it's covered by whatever you bought for a neighboring country, avoids the problem entirely.