1. Roll it into a traditional IRA, and if you're going to convert to Roth, wait until a year that you're in a lower tax bracket.
2. Generally, you should treat all of your tax-advantaged retirement accounts as one large portfolio with separate accounts. I suggest picking a desired asset allocation and figuring out how to best implement that across your IRA, Roth IRA, and 401(k). Are you comfortable at 100% stocks? I don't see a significant upside to 100% stocks versus 80% stocks and 20% bonds, and plenty of downside.
3. Reasonable people differ on whether or not the taxable investments - which are to be used to retire at a reasonable age instead of 59.5 or later - should be treated as the same portfolio with the tax-advantaged accounts. But that's another story for another time.