You don't have to use ebay's program. You can ship directly via USPS or other label providers (stamps.com, pirateship). Just make sure that you don't have Romania excluded as a shipping location.
When you ship directly, i.e. not using ebay program, make sure that the commodity you are selling is not prohibited. Also, you need to fill out the customs form correctly, especially the IOSS number which ebay provides when an international purchase is made. (that number for EU is: IM2760000742). Also, you need to provide a so-called harmonization number, HS code, which for EU consists of 10 digits. The description of your item has to be very specific, if you are mailing a shirt, don't say clothing but shirt. If you follow this, you won't have any problems with the customs.
I don't use ebay's program, and have had zero problems with international deliveries, including a recent one to Romania.
