It sounds like you are looking more for a book on Roman history than Roman coins. Many Roman coin books do include a lot of history, but most are primarily a catalog. The list of Roman history books is nearly endless. For coin books, most that include a lot of history and background cover only a period of history and you have to buy many volumes to cover the entire series.
It sounds like you and I have a similar perspective. What I enjoy about ancient coins is researching them and I don't mean just the coin itself. I will frequently start with the coin and then search for information on the year the coin was struck, or the person depicted, or the god or goddess depicted. I do much of this research online, using just Google.
There is much research, including scans of entire books and links to many more on NumisWiki.