How to balance Roth IRA and 401k as one lump sum?

I read on here recently that it's preferable to keep bonds in my 401k rather than in my Roth so that the Roth can be focused on the most tax advantaged growth. First, is this true / worth the effort? And second, how can I easily balance it to do this? Or do I just need to do some math? Right now I try to keep a 60/40 split between US/International and then about 10% bonds total. Having it in separate accounts is easy because Fidelity just says my percentages... 54/36/10 for example. If I treat the accounts as one big lump sum though that equation gets a little bit more complex obviously.