You don't need sentries to protect your own jungle. Just a couple of observer wards. Techies needs to be physically present to drop a mine, you can see it and have a rotation to punish him immediately.

If you warded your jungle but not your triangle and your carry goes there after 10min of no techies on the map, well, you got a carry problem, not a techies problem.

As for moving in their jungle/tower/Roshan, illusions, sentries, necro3, pipe of insight, infused raindrops, aeon disk, glimmer cape, etc... Talk to your other support.

If techies is reduced to blows up camps in their jungle or creepwaves, he will famish his own cores. It takes times to make a ultrakill worth stack of mines so if one blows up, the tier of towers behind or the one on the other side of the map will probably not have some.