Arsenal
Arsenal need to improve their attack, and make sure to score as many goals as the opportunities as they create. If Arsenal gets a good striker in the transfer chance and get reinforcements in some other positions in the team, their chances of doing very well in the champions league round of 16 more than they did in the group stages will be higher. I see Roma coming to the champions league next season, I see Mourinho as someone with a plan, they look to be on that track already to achieve that with their current position on the table.
Getting a new good striker is one of the anticipation we are keeping on the gunners by the next transfer window, it's very much needed if the gunners will further go beyond the round of sixteen in the UCL this season because the need the goal advantage as much as they also need the wins in this league so far.
Roma coming to the champions league next season is still under great probability because even currently they are not in a very consistent form, they don't have the ability to maintain a position around the top four and they seem yet to have a particular form which will help their performance on the pitch, I think Mourinho is still at the building stage with this team and until he gets it's right there will be no much difference from what they have now and making it to the champions league next season won't make sense because they will not be able to make anything good out of the UCL.