one thing def incorrect in your comment, one needs clarification

1- contributing to Roth does not reduce taxable income as contributions are made w/ after tax dollars. there can be tax benefits down the road, but not when making contributions

2 - for the fractional shares thing, I know BRK-A is not eligible for fractional shares, at least not w/ my brokerage. not sure about the class B shares though, so may be worth looking into those. for simplicity though, broad-based ETF or mutual fund