It is very difficult, perhaps impossible to carry out an invisible repair on any roughcasted/tyroleaned/ textured surface. You will always see it, no matter how well it has been patched, but with a little bit of work it can be blended in, and made to look ok. If the cement render patch has been reasonably done and not built up around the edges,and onto the original tyrolean finish (t/f), you can mask off the t/f very slightly beyond the cement render patch,and spray on a couple of thin coats just to build up the t/f on the cement render patch itself.When you are happy with the build up, remove the masking and give a little spray 2 or 3" onto the original t/f to blend it in,,,but,,,,,
short of doing the whole wall again,, that is about as good as you will get..... You will also see the difference in colour between the new and old t/finish, but you could always paint the wall sometime if need be.
Roughcaster.
