Although with the 3D TV being spaced apart and imparting more direct force, wouldn't that reduced roll effect be negated? I may just be imagining things but I thought that was one of the reasons MiG's and Su's have their nozzles further from eachother compared to western fighters
Your argument has some scientific but not historic basic.
MiG-29 and SU-27 were designed well before trust vector control as we know it today. The reason there was survivability from a catastrophic failure of one engine affecting the other. The russians has always like to build planes that are are likely to be shot at before they can shoot back. Whether that's operational pesimism or simple pragmatism, otherс more qualified here can tell.
Regarding the roll rate influence.
If spacing the engines ever further оут did increase aircraft roll rate, we would be seeing a lot more configurations of fighters with engines on the wingtips
The truth is that, aerodynamic surfaces provide just as much control authority without the accompanying weight. You just need to keep the wingspan short. The easiest to maneuver design is the one that has it mass as close to its center of gravity as possible.
The main reason for spacing of the engine on the T-50 is not to enable better use of trust vectoring in roll (that is a side effect) but to create a space where the main weapons bays will be located. Their configuration is the main design driver of the T-50.