Pattern of naps for 4 -5 month old? And what about rolling over?

[firstpregnancy]

DS is 19 weeks old and has been a really good sleeper/napper since he was born. However, he rolled over for the first time yesterday and this morning would not go down for his nap. He normally goes down about 15 minutes before he goes to sleep and usually has his first nap of the day (45 mins long) at about 8.15 until 9am. However, he has only just gone to sleep ? it is 10am.

He keeps trying to roll over in his cot but can only get so far and he can?t roll back so I have the dilemma of whether to leave him to try, or to go in and move him back as soon as he does it (I wouldn?t let him sleep like that yet, as he can?t roll back). Don?t really want him to be practicing rolling over at nap time, yet I don?t see what I can do about it as he has a go as soon as I?ve left the room, so would be in and out all the time.

He has been having 4 naps of about 45 minutes in length (usually can stay awake for 1 hour before first nap, then 2 hours for the other three). Is it likely that he may be starting to change his pattern?

People have been telling me that he may start to consolidate his 4 naps when he becomes more active and only have 2/3 longer naps. Could this be the start of it? When did your DCs go from 4 naps to 2/3? And how long did these naps last?

I am dreading that this is part of the 4 month sleep regression and really, really hope that his night time sleep isn?t too affected by this.