You have it backwards - the Traditional saves taxes now, Roth saves taxes later at the expense of paying more now, and having a 401K only impacts your IRAs in that you have a lower limit to make deductible traditional contributions.
The Roth vs Traditional (assuming you are actually eligible for both - in tech you might be making enough money it really isn't much of a choice) has to do with what your marginal tax rate is today vs. what you think your effective tax rate will be in the future. So if you've already managed your AGI down to the 0% tax bracket, before making the IRA decision, then for sure go Roth. Above that, you've gotta decide. A lot of people draw the line between the 15% and 25% brackets - if I'm in the 15% I go Roth, in 25% Traditional (to the extent I can).
Personally I've come to the realization that we can likely pay 0 to very little income taxes in retirement, assuming the basic tax structure remains the same, so I put as much into traditional retirement accounts as I can. So happens we now make so much money that on the IRA side, the Roth is where we have to go - believe me, if there was a way to do it, I'd be putting IRA contributions into traditional. Falls in the good problems to have category.