As per MDN on <input type="number">:
The implicit role for the element is spinbutton.
So as long as you didn't change the role by means of a role attribute, this is the correct role to use in getByRole('spinbutton').
An input number is like a counter, so it is spinning its values up and down by clicking in the spin buttons on the right side or the keyboard arrows, (even its pseudo elements are ::-webkit-inner-spin-button, ::-webkit-outer-spin-button).
If this is surprising to you, that input type might not be the right choice for the form control. The documentation reads further:
If spinbutton is not an important feature for your form control, consider not using type="number". Instead, use inputmode="numeric" along with a pattern attribute that limits the characters to numbers and associated characters.
The number input has several accessibility and usability issues when used for anything that is not a floating point number.
Update (based on OP comment)
So would userEvent.type work on it since it is a spinbutton?
Yes it will work, here is a sandbox with a basic example

import { render, waitFor } from "@testing-library/react";
import userEvent from "@testing-library/user-event";
import "@testing-library/jest-dom";
it("should type a number in input", () => {
const { getByRole } = render(<input type="number" />);
const input = getByRole("spinbutton");
userEvent.type(input, "123456");
waitFor(() => expect(input).toHaveValue("123456"));
});