A guest will have hard time in a home away match and Roma will be the host in this match. They can use their two matches with Leverkusen last season as own lessons and take them as one of their preparations for this match. Leverkusen didn't have too many changes in their players since last season so even they upgraded themselves a lot, there will be some common things with the past season.
Leverkusen must play very carefully and avoid mistakes like in their match with Qarabag FK because Roma are at a higher level than Qarabag FK and can beat Leverkusen and won't allow Leverkusen to equalize the match easily.
At least it affects playing away but if the team has a strong mentality I don't think it's a big problem and so far Leverkusen is a team that has proven that they have a strong mentality, Leverkusen is a team that is unbeaten this season in all competitions.
Leverkusen, who will play away in the first leg, will of course make a strategy to make it easier for them in the second leg. I think a draw is good enough for Leverkusen if they can get it and try to play optimally in the second leg at home.