Adobe Arabic text with English numerals

Well, I'll be honest with you - I always fix those digit rendering issues after the fact. I format stuff in Arabic by a wide variety of translators, and those translators have a Very Wide Variety of levels of technical skill. So, when they're working in MS Word, some of them will key in their translations so they place perfectly in InDesign. (You are using File -> Place, right, not copying and pasting?)  Others have... less technical skill. They'll do things like key phone numbers in backwards so they render correctly in Word. Or they'll input one RTL open parenthesis, and they'll forget they switched keyboards from Arabic to English, so their "close parenthesis" will actually be a LTR open parenthesis. All this is complicated by the fact that Word and InDesign handle bidirectional text differently, so there is no single check box that will fix all of your dates and phone numbers and parentheses et cetera. 

So, post-import cleanup is how I advise people to handle it. If your text is marked as Arabic, and your digits are marked as Default, then you won't have any Arabic numerals at all in your document. (These are AKA "english/roman numbers" but I'm fairly sure you don't mean that because Roman numerals are I II III IV V VI etc.) If you want to keep those digits as Arabic numerals instead of Hindi numerals, there are a bunch of ways to handle that. I like using the Middle East Character Formats section of the Paragraph style. Or, if you are one of those people who does everything by hand and won't use styles, then a) consider joining us in Team Using Paragraph Styles All the Time, and b) do a GREP search for 

\d+ 

which will find all groups of digits. You can then use the Change To Format section and specify Arabic Digits and Left to Right display: 

Not to worry, we have a few of them over this side of the pond too Steve.