The pro rata calculation of your Roth conversion(s) does not depend on the relative timing of the conversion and rollover transactions. The Roth conversions are essentially treated as having occurred on December 31. The result of rolling over the 401(k) to a traditional IRA has made your Roth conversion largely taxable, with a large portion of your basis in nondeductible traditional IRA contributions remaining with your traditional IRAs (line 14 of Form 8606) to be applied proportionally to future traditional IRA distributions.
