I agree with you, I believe the parallels between Luffy and Roger are only starting to be revealed. Obviously they have the same child-like enthusiasm, love for freedom, and an odd relationship with the marines. On the other hand, we have next to no knowledge about his fighting style. Based on how Rayleigh describes him, it might be safe to assume that he could be just as reckless in battle as Luffy is. He did decide to go to Skypia after all. Furthermore, with what we have recently learned about Devil Fruits being reincarnated, what if there is more significance to Shanks finding the Gomu Gomu no Mi. That Roger's apprentice finds the same fruit he had eaten, and passed it on to the individual who most greatly resembles him. Finally, what if it is the recklessness and the Gomu Gomu techniques are what led or will eventually lead to their deaths.