> Early investors often have a ROFR (Right of first refusal) in their share agreement, in which case they will have the right to buy shares proportional to the amount of dilution they would otherwise suffer (so they can maintain their % stake in future funding rounds) but I've never heard of an employee having that right.

FWIW, what you described isn't right of first refusal. ROFR specifically refers to the right of an existing investor to buy shares when another investor wants to sell to a third party. E.g., let's say A has a right of first refusal, and B wants to sell at $20 / share to C. With ROFR, B must offer $20 / share offer to A first.

The right to buy shares proportional to existing ownership percentage is called a pro rata right. If a round of funding would dilute your 1%, you have the right to buy in at the pricing of that round to keep your percentage ownership constant.