Can I rollover the 401k with my current employer to a solo 401k that I start with my business?  

But If I were to roll over my IRA into a Roth next week would my tax bracket be at 100k or still 50k?

ROBS or rollover as a business.

We are looking to rollover his 401K into an account we can use to invest in real estate.

It was a rebuilt rollover that sat in a barn for years.

There is another program known as a Rollover as Business Startup that would allow you to use retirement funds to capitalize a real estate development company that you can be directly involved in.  

If you are eligible for a Solo 401k plan you can rollover funds there and take a personal loan form it (limited to $50K), which can be in turn use to make personal investment. 

Often times you cannot roll over the investment plans until you are no longer employed with the company.

I'm looking to roll over a previous employer IRA into a SDIRA.  

However, in that case and if you are self-employed with no full-time w2 employees working for you, you could set up a Solo 401k with a provider that allows for 401k participant loans, rollover the funds and then take a loan from the Solo 401k.3) Here are the general considerations regarding 401k loans.401k Participant LoansIf your 401k plan allows for 401k participant loans, the maximum loan amount is equal to 50% of the balance up to $50k.