How is the overall rating within the depth chart section being calculated? It says by depth chart position but does this mean that the overall rating is being calculated by some pre-determined weighting as opposed to a specified "player role" weighting? None of the ratings match to my player role ratings.

Mine is the same as the player ratings

The overall ratings are the same in my Depth Chart and Manage Roster sections. However, they are not the same as my Your Player Roles section (including the system roles). This difference makes me wonder how they come up with the Depth Chart overall ratings if they are not using the system roles. It does look like the overall rating in "Your Player roles" takes into account the FT rating. Maybe this is the source of the difference?

The rating within the depth chart is based on your user setting for Overall Rating, if you have it set to Use Player Roles then the players will use whatever player role is assigned for the position he is listed in the depth chart as.

So to clarify, lets say you have a PG named Rob Smith. When he is listed in the depth chart under the PG position, the rating you see for him will be his rating adjusted for your PG player role. Then if this same guy is listed somewhere in the SG position, the rating you see for him will be his ratings adjusted for your SG player role.