I am a sole proprietorship. It seems like it would be a good idea to roll my existing IRA into a 401(k). I would then like to convert the new 401(k) to a ROTH 401(k). Other than paying the taxes on the conversions, what would be the cons and pros of this strategy?

“ It seems like it would be a good idea to roll my existing IRA into a 401(k). I would then like to convert the new 401(k) to a ROTH 401(k). Other than paying the taxes on the conversions, what would be the cons and pros of this strategy?”---->I guess as you can see, you, as a Sole proprietor, are eligible for an Individual(Solo) 401k provided you have no W-2 employees (other than your spouse) who work more than 1,000 hours per year. You may be able to contribute as much as $40,000 a year to this kind of plan. However, if you plan on hiring employees later, you will want to think carefully about this because you'll be required to expand this to include the employees(you will have to convert the individual plan to one that covers everyone). 2 primary advantages of the Individual 401k versus other sole proprietor retirement plans ; potentially greater retirement contributions at the same income level, therefore maximizing retirement contributions and valuable tax deductions.; therefore the Individual (Solo)401k is usually the best sole proprietor retirement plan for maximizing retirement contributions and valuable tax deductions while reducing income taxes. Another major advantage of Solo 401K is the option of a loan up to a maximum of $50,000 using your Solo 401k balance as collateral for the loan. Solo 401k loans are permitted up to 1/2 of the total balance of the 401k up to a maximum of $50,000. The proceeds from an Individual 401k loan can be used for any purpose, there are no income or credit qualifications to receive the loan and interest and principal are repaid to yourself. A loan from an Individual 401k is received tax free and penalty free. Loans are generally repaid monthly with a 5 year loan term. There are no penalties or taxes due provided loan payments are paid on time. Unlike the traditional version, the solo 401k is inexpensive to create and administer. It is entirely possible that the Solo 401 (K) plan is the best choice for entrepreneurs who work alone and without employees because of their relatively simple in nature, and are not expensive to create and manage.
I guess R401K ,like Solo-401K, is streamlined, inexpensive and can provide great benefit. R401K often permits greater contributions for retirement than might be available under different sorts of plans. Under a Roth structure, earnings can be devoted to retirement on an after tax basis. As a counterbalance, the funds so invested grow tax free and face no additional taxation upon withdrawal. A Roth version of a solo 401k would appeal to taxpayers who anticipate that their tax rate will increase in future years,MUCH like R-IRA plan, those likely to make significant gains in their retirement accounts over time, those who desire to pass assets to their heirs tax free, and those with incomes high enough to disqualify them from Roth IRAs. This type of plan, like Solo 401K plan, is extremely easy to administer, as they necessarily have a very limited number of participants. This fact alone removes a host of normal rules and regulations that might apply. I guess you may need to contact your retirement plan planner.