Rolled over Roth 401k into Roth IRA. Didn't realize employer match was pretax.

Although it seems it may be common knowledge, I was unaware that not all of the money in my Roth 401k was Roth. After I left my previous job last year, I rolled over my Roth 401k (& employer match) into my Roth IRA with Vanguard. As you can guess, I have a fat tax bill on the employer match portion of my Roth 401k. Is there anything I can do at this point (i.e., request the money be transferred from my Roth IRA to my IRA)?

If not, so be it. Hopefully this post can help somebody else avoid my mistake.