Your best bet is to call CO and request availability on LH or UA to Europe. You are CO Plat - so you will get better availability on CO flights - but CO does not open inventory as soon as others.

So book your reward tickets on LH to FRA or MUC with connection to Rome, then you can always switch to CO if it opens for no fee (since you are Plat). UA goes out of IAD.

What you might want to do is try to get International F - not business, and all CO has is business. Both LH and UA have International F service. Will cost additional miles, but looks like you have it.

You can check reward availability for *Alliance by checking ANA site, but you need to open an ANA account first.

Welcome to FT!