Yes, PAYROLL is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, Y 4, R 1, O 1, L 1, L 1.

Is it a valid word?

PAYROLL is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a list of employees and their salaries
the total amount of money paid in wages
the department that determines the amounts of wage or salary due to each employee

Also: payroll department.

Not playable in Scrabble US: PAYSHEET.