Attacking weak PRNG Math.round(Math.random() * 30D)

Is it possible for an attacker to predict, following a random generator of the form Math.round(Math.random() * 30D), with a sufficient number of values? I know that the Math.random is a weak PRNG, but does rounding up the value not prevent brute force attack or analysis (as there are many on this PRNG)? And if that does not stop, how could the attacker proceed? Thank you in advance for your answer.