There is a book called Roman Woodworking by Roger B. Ulrich. It is available on Amazon but it is very expensive about $500 for a new copy. However if you subscribe to Scribd it is available there. It covers tools & woods used, the best time of year to cut etc. I found some information from the book which covers a bit of what you wanted to know.
Drying, Preservatives and Conditioners
Drying by application of heat.
Columella De Re Rustica. 1.6.19: “the smoke room too, in which timber, if it has not been cut for a long time, may be dried quickly, can be built in the part of the country villa next to the rural baths.”
Treatment by charring.
Vitr. 1.5.3: (on binding and reinforcing the outer and inner walls of a defensive circuit): timbers of charred olive wood should be frequently placed [transversely] in order that both facades of the wall as if connected by pins...may have everlasting strength. For such timber cannot be injured by decay, weather or age.
Treatment by oiling.
The use of cedar oil on wood:
Plin. HN 16.198: “timber daubed with cedar oil suffers from neither worms nor decay.”
The use of amurca (the by-product of olive oil production):
Cato Rust. 98.2: “lest moths ruin clothing...rub the exterior of the bottom, the feet and the corners of the chest with [amurca]...If you rub wooden furniture all over with amurca it will not decay, and so treated will shine more brightly.”
Treatment by smearing with or immersing in dung:
Cato Rust. 31.1 see fibula under ÏV.2 Joints.”
Plin. HN 16.222: “we have in our country some timbers that check[split] by themselves, on account of which architects prescribe that they should be smeared with dung and then dried, so that drying winds will not harm them.
Treatment by immersing wood in saltwater:
Plin. HN 13.99: “the shattered remains of ships have recently shown that this timber, dried by the action of seawater, is solidified with a hardness that resists decay more strongly than any other method.”
Treatment by drying wood in piles of grain and burying it in earth:
Plin. HN 13.99: “carpenters lay citrus wood in heaps of grain for periods of a week with intervals of a week between, and it is surprising how much weight is reduced by the process.” In the same passage Pliny reports that some barbari (probably North African Mauretania) where citrus wood was harvested they treat the raw timber by coating it in wax and burying it in the ground.
Regards
Michael Kerr