This faience bead (currently housed in the Hunterian Museum in Glasgow) is the typical blue-green color of most faience beads (though I’ve seen some that are a darker green and others that are almost yellow or brown). The faience has degraded over time, so the color is not as bright as it probably was in the past, but you can see flecks of the original turquoise color in some of the grooves.
Faience melon beads, like this one, are generally assumed to be Roman. The Romans often used melon beads, and they often used faience melon beads, so while others may have had faience melon beads, they’re generally associated with Roman culture. For a Roman bead to be in Scotland, it’s probably dating between 100 and 400 AD.
In Scotland, faience melon beads are only really found at sites with known or suspected Roman occupation. If the occupation is suspected, it’s suspected for reasons independent of the faience bead(s).
In fact, here’s a map I made as part of my research into beads in Scotland. Each point shows a site with one or more faience beads.
For those who know some of the ancient geography of Scotland, you’ll notice that all of the sites with faience beads fall directly between Hadrian’s Wall (which is essentially the modern border between England and Scotland) and the Antonine Wall (essentially an invisible line between Glasgow and Edinburgh). These walls were both Roman, and mark the primary region of Roman presence in Scotland.
The fact that these beads are only found within Roman boundaries and not outside them seems to uphold the idea that these beads are Roman. However, that doesn’t necessarily mean they couldn’t have been made outside of Rome and simply used by Romans. Or perhaps Romans made the beads and traded them within their borders, but not everyone who used these beads saw themselves as Roman.