I've chosen to roll with mostly white belts recently so that I can take my time and roll with a little less intent allowing me to protect my shoulder injury as much as I can. 

I've noticed a few times with some people I am rolling with - they apologize for either lack of technique or strength or endurance...or something. I probably do this too when rolling with more advanced guys at times.

The thing to remember is that the more advanced practitioner is probably sharpening a particular part of their game or developing a new one. Rolling with a person with alot less skill offers the chance to be more dynamic and try transitions and submissions that in a roll with someone of equal skill and size - you simply do not get to do. So yes there may be an obvious gap in ability but each person, guaranteed, is taking some benefit from the sparring session so there is really no need to say sorry for anything...

...then again...it might just be a Canadian thing... 

• Washing your GI (2009-12-09)
• Challenging a higher belt (2009-12-06)
• T.U.I - Training Under the Influence (2009-11-24)
• Late for class (2009-11-23)
• Rolling when tired (2009-11-23)