Russian olive around here (eastern US) refers specifically to Elaeagnus angustifolia. It is a very hardy and invasive species that is taking over large tracts of land (including my back fields). There is a similar species often called autumn olive which is Elaeagnus umbellata. Both are types of “silverberry”. I have a potted one which I keep with my other hardy trees, it is exposed to temps well down into the 20s (F) and is fine with that. Could probably handle even colder than that when potted. Both of these are deciduous and will drop all leaves in winter.
Other “silverberries” aren’t as hardy. For instance, one of the more common varieties used for bonsai is Elaeagnus pungens. I have one of those and I keep it in a warmer location during winter, it does get some freezing temps but not much lower than the upper 20s and not for long periods. I don’t know the exact cold tolerance but am not interested in testing its limits! This is more of an evergreen species.
These can be tough to tell apart but if you were to put E. pungens next to the others I think it would be obvious. One difference is E. pungens blooms in the fall and the other two are spring bloomers, though flowers are similar.
Don’t know if that helps or not. Do you have any pics of the leaves, flowers or fruit of yours?