Should the roll overs from my individual 401k and my individual roth 401k into my roth IRA ( all accounts at Vanguard ) be a taxable event?

Yes. A traditional individual 401k (funded with pretax money) rollover into a Roth 401k (funded after-tax) is taxable. A Roth 401k to anything Roth is not taxable. Both, however, should be reported to you on a 1099-R and by you on your return.

Please feel free to post any additional details or questions in the comment section. 

My 1099R forms for the both rollovers do not list a taxable amount in box 2a and show G in box 7 for distributions. Vanguard informs me that a form 5498 will be sent in May. How should I proceed in TurboTax to show a taxable amount for the individual 401k rollover to roth?

Fill out the 1099Rs exactly as shown on the printed form. You'll have follow-up questions to say that your roth to roth was rolled over and how much was RO'd. Let me know if you need more instructions there.