I ll add that these were called Hindi numerals by Arabs themselves ( Indian numerals ). And add that numerals are just a feature the more important arithmetic techniques.

It’s the place value of the Indian arithmetic system that the numerals facilitated which was much more interesting. place value means that the numerals had varying values depending upon where they were placed in a number as in, 1234 : 4 had the value 4*1 =4. 3s value was 30, 2s value was 200 and 1 was 1000. Thus making a number : one thousand, two hundred and thirty four. This did not exist in the Roman numerals, while a base 10 system. 0 also did not exist in the said system.

You could argue the ease for any base system with place value and zero included and carry out the calculations with the same ease - and they are carried out of course. binary arithmetic for example, in computer systems today.

Without the zero and the place value the arithmetic becomes way more tedious. It does not scale. Since you have to physically count everything. The counting is not intuitively tied to the numerical representation of the numbers involved. You can’t use the well known techniques of carries and borrows. That is, you can’t use the now traditional way of adding, subtracting etc without the zero or place values.

The base ten has the advantage in being intuitive. And the decimal system where each of the ten numerals have a place value is an innovation that makes things much easier in terms of arithmetic techniques.

The decimal arithmetic had the advantage of being able to be carried out on a piece of paper with much more ease without the need of an abacus. It also scaled well on much higher numbers. ( evident in the numbers medieval Indian mathematicians dealt with - have names for. That would be a book in itself, but the point is, these numbers become less daunting in the arithmetic explained above while they’d be nightmarish in some other systems )

As for when they were introduced to Europe I don’t know exactly. And I ll leave it for someone else to answer but I hope I have answered the superiority of the decimal system ( or any base system that includes a zero ) compared to Roman arithmetic. That is the answer to why they were used instead of extant numerals.

Edit : grammar

Edit 2 : you can see that while Greek Roman geometry and thus architecture reached great heights, the arithmetic remained very limited. It was the techniques involved that were limiting. One sees this in the later history of mathematics elsewhere. Most notably in newton and Leibniz independently inventing calculus but continental calculus far eclipsing British work because of the notation system of Leibniz.

Edit 3: a bit more on place value for the interested : let’s take a base other than 10. Let’s take base 4 system where we have four numerals 0123. So a number like 123 is thus

14^2 + 24^1 + 3*4^0 = 27 in decimal. So from right to left the power of the base in the multiplier increases by 1.

Addition would be thus : 122 ( 26 ) +313 ( 55 ) —— 1101 ( 81 )