DH and I have our Roth IRA accounts with Fidelity. Right now it's all in the Fidelity 500 Large Blend fund (FUSVX). Once we contribute for 2017, we'll have enough to divide each of our accounts between that fund, small cap (FSSVX), and mid cap (FSCKX). I'm trying to keep expense ratios low (< .1%) for the Roth IRAs. My 401k and DH's 403b have a higher expense ratio (.67% and .31%) given that they are target date funds through our employers.
Are there any other index funds to consider or is this diverse enough for our Roth IRA accounts? TIA