The match is expected to end with a draw in this first leg and both teams to score according to some predictions I saw. Well, Roma is playing home and will have hard time against Bayer Leverkusen. Personally I think Leverkusen are favourite but maybe the fact they are playing away will contribute to the suggested draw.
For both teams to score, I think it will be accurate and at the end Bayer Leverkusen to pass if they could secure any result other than a defeat in Rome.
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.