Can I use Deore RD-T610-SGS derailleur on my road bike with 105 shifters, it seems like cable pull isn't right. Shifters are on 2007 Specialized Roubaix compact.
Actually, I use a 9-speed mount derailleur (deore xt) on a 10 speed cassette (11-32) with a 10 speed road shifter (105) and a triple (50/36/30). The cable pull is fine. The capacity is just OK. It took some b-screw adjustment to get it working well.
It turns out there are many people doing the same thing, especially on tandems.
This fits what you said - but it is notable that one can still run a 10 speed mountain >cassette< with a 10 speed road shifter.