How to roast "per pound" if weight is 7.27 pounds?

Always go by temp. Everything else is misleading. A thermometer is investment for an excellent result.

Well, it depends on how much math you wish to do and if you'd prefer to use paper or a calculator. So ".27" is a decimal with a fractional equivalent- 27/100, to be precise. That gets multiplied by x/16, and with a little math magic, you will arrive at 4.32 oz. So a total of 7 pounds, 4 and roughly 1/3 oz. That is part of the reason why metric weights are used when things need to be exact. But luckily for you, cooking is mostly art, supported by science, and you do not have to be that exact and precise. You could simply figure that your weighted item is 7 pounds and a shade over a quarter of a pound. (.27 being just a hair over .25- which is a quarter, or 1/4 of a pound) Figure out how long it will take for the 7 pounds, multiply the time per pound by 7. Then divide the time per pound by 4, and add that to the time for 7 pounds. That gets you into the target time you will need, give or take a few minutes. You can't get exact timing anyway, because ovens vary, meat density can vary, etc etc. Which is why the other most helpful item in your kitchen is your thermometer - which is the best way to judge when an item is cooked appropriately.
As a rule, roasting does not require such exactness of weights and measures. I suspect most ordinary folks simply ignore the additional fractional measure, or perhaps do what I do- which is to consider it a hair more than a quarter of a pound. I can divide most things by four, so it's not a big challenge for me- if I think it's that critical. But honestly, I just use a thermometer when I am closing in on the time I think is close to correct- and let that be my final guide. You just can't cook everything by a clock, after all. Roasts don't wear fitbits.