It depends on the dice, and how you use them.

As an extreme, imagine a poorly constructed die that is unevenly weighted and rolls a two 50% of the time when thrown randomly.  Also, imagine always holding the die a half inch from the table with the number two facing upwards and then just dropping it.  Clearly, neither of these would result in much randomness.

If you are confident that you have "fair dice" (each face has an exactly equal chance of showing up when tossed randomly), and you are confident that you have come up with a reasonable method of tossing the dice in a random way, you have one other issue to consider.  You might think to save time by rolling multiple dice simultaneously.  However, if you do this, you need a way to make certain that you are randomly recording the results of each throw.  If you always record them from smallest value to largest (or largest to smallest) then you will have lost a LOT of randomness.  If you try to force yourself to choose at random, you may be subject to unconcous biases that you are unaware of.

Assuming that you've overcome biases in dice manufacture, and in your tossing method, and in your recording method, then dice could possibly be a good source of entropy.