is there a way in Roman script for distinguishing in a compound the result of -aḥ + vowel other than a which could be i  =  a i, with hiatus, from the diphthong ai resulting from a/ā + e/ai ?

ex. manaḥ + indriya- = manaindrya- (?) beside mānasa + aindriya = mānasaindriya

In nâgarî script I find written mana indrya- with a space put between the two members, but it would look strange in Roman script.