turnover rate and roth ira

Not an expert but I believe turnover rate is only one consideration that is part of total return. A mutual fund, just like you or me, will encounter higher expenses if we trade a lot. Also, a lower turnover rate may indicate a less active management style. For example, an index fund. If a mutual fund has a high turnover rate and a high expense but beats the crap out of a low turnover, low expense fund in total return then it still wins in the overall return game.

Correct. A higher turnover rate leads to higher capital gains taxes. In a Roth, these are irrelevant. Same reasoning applies for a fund that spits out a lot of distributions.

ETA: but this is only part of what contributes to the expense ratio