Depends on the technology. Sure, for steam engines you need good metallurgy, but it turns out that good metallurgy needs relatively little in the way of technology as opposed to knowledge of chemistry and minerals. With the knowledge of chemistry available in 2012, it's very, very easy to move Rome forward to late 190th-century steel metallurgy. Bessermer converters and open hearth furnaces are reasonably within the capabilities of Roman brick technology to build; they just didn't know enough about the chemistry of steel to know what they should be making.