My BowlingGame Kata (still no OOP, but with some improves)

BowlingGame.java

package com.tolbier.bowlinggamekata;

public class Game {

	private int currentRoll = 0;
	private int rolls[] = new int[21];
	int rollIndex ;
	public void roll(int pins) {
		rolls[currentRoll++] = pins;
	}

	public int score() {
		int score = 0;
		rollIndex = 0;

		for (int frame = 0; frame < 10; frame++) {
			int frameScore = getFrameScore();
			score += frameScore;

		}
		return score;
	}

	private int getFrameScore() {
		int frameScore = 10;
		if (isStrike()) {
			frameScore +=  strikeBonus();
		} else {
			if (isSpare()) {
				frameScore += spareBonus() ;
			}else {
				frameScore = sumOfBallsInFrame();
			}
			rollIndex++;
		} 
		rollIndex++;
		return frameScore;
	}
	private  int sumOfBallsInFrame() {
		return  rolls[rollIndex] + rolls[rollIndex + 1];
	}
	private  int strikeBonus() {
		return  rolls[rollIndex + 1] + rolls[rollIndex + 2];
	}
	private  int spareBonus() {
		return  rolls[rollIndex + 2];
	}
	private boolean isSpare() {
		return rolls[rollIndex] + rolls[rollIndex + 1] == 10;
	}
	private boolean isStrike() {
		return rolls[rollIndex] == 10;
	}
}

with a Java "structured programming" schema, and with respect and devotion for "UncleBob" Original Kata, but in favour of cleaning, I think it could be improved as it is here