Did the Romans have a Latin word for 1000 years?

They did not have one single word like we do/Neo-Latin did with millennium. When Cicero talks about "thousands of years", he simply says multa annorum milia. One workaround later authors used is the adjective miliarius.

1. What is Latin for 1000 years?
2. What is 10 000 years called?
3. What is the ancient Roman word for year?
4. How many Latin words are there?

What is Latin for 1000 years?

Since in Latin mille means "thousand", a millennium lasts 1,000 years.

What is 10 000 years called?

10,000 years is called 'decem millenniuum' or myria-annum (though these are not commonly used).

What is the ancient Roman word for year?

Latin is very rich in words. So most often you have many words to say a single word. To say years in Latin, you have Anni, Annos, Annorum, Annum, and Annis.

How many Latin words are there?

Latin is a dead language. That's an advantage. In total, there are about 30,000 Latin words in classical writing, and I'll make a bet that we aren't finding a lot more where that came from.