Eddis, Attolia, Sounis

You could follow up Eagle with The Silver Branch and The Lantern Bearers. They're not directly connected, but are sold as the Roman Britain trilogy due to following the same family line through three different periods in Roman-British history. I love Lantern Bearers, though I warn you, Sutcliff's writing doesn't always end on a happy note, so have tissues and chocolate at the ready.