Part 1 - Make it work for a single selection and related role
Create a rule which looks like so:
- Rules Event: After saving user profile.
Rules Conditions (both conditions must be satisfied):
- entity has field (with the field corresponding to (eg) "Automotive".
- data comparison to check if "Automotive is selected/checked".
Rules Action: : Assign role to user (for the role related to "Automotive").
You could create a similar rule for each possible combination of checkboxes and roles to be assigned. Or continue as detailed in Part 2 to further enhance your rule from Part 1 so that you end up with a single rule for all possible combinations.
Part 2 - Make it work for other possible combinations
To also make it work for other possible combinations, and because of the fact that a Rules action cannot contain "conditions", you basically have 2 possible approaches:
- Create a similar rule (as in Part 1) for each possible combination.
- Use the Conditional Rules module to enhance the Rules Action in the above rule to alter the flow, using either Conditional (if/else) of Switch logic. Be aware: this module only has a beta release for D7, though it's used in over 8K sites (which makes it seem like a pretty robust module though).