Ironically, I remember early in the life of 4e reading the point being made strongly by WotC that the design was supposed to make sure that 'whatever you chose to do with a class, it would still be good at its primary role' - which over time somehow morphed in peoples perceptions to 'your class is mechanically locked into a role'.
Now, it may or may not be that designers after the initial design didn't grok that and ended up introducing stuff which had the effect of locking people into a role. I don't know enough to judge - but it wouldn't be the first time that original design principles got undermined, and it won't be the last either!
I have said in another thread that roles seemed to be the alignment of 4e: it's as if "You can't do that, you're [role]" killed "You can't do that, you're [alignment]" and took its stuff.
Roles tell you what your character is good at. They don't prevent you from doing things that you aren't good at, any more than being untrained in Stealth prevents you from hiding, or being untrained at Perception means you can't notice things. If you're not a striker, you can still deal out damage. If you aren't a defender, you can still get between an enemy and a badly wounded ally, and be no worse off than any character in any edition who doesn't have a mechanic to make the enemy want to attack you instead of your ally.
Now, one possible source of unhappiness about roles is that they make the classes more inflexible: if all characters of a particular class are a particular role, then you're not playing that class to its full potential if you don't want to take on that role, e.g. non-Defender Fighters and non-Controller Druids. IMO, the solution to that is not to ditch the concept of roles, but to make the classes more flexible, e.g. the Essentials Slayer Fighter and Leader Druid.
Fairly or not, I'm sure that there's been too much of a public backlash against roles that they will likely not be explicit in 5e. However, I'm sure that they will be there, "under the hood" so to speak, as they are far too useful a design concept to ignore.